Materials design for new functional
semiconductors by ab initio electronic
structure calculation-Prediction vs. experiment-

Hiroshi KATAYAMA-YOSHIDA*, Kazunori SATO* and Tetsuya YAMAMOTO**

The use of ab initio calculation for materials design is an interdisciplinary researchthat bridges between computational physics
and applied physics. It will become indispensable for future generations in the 21st century where there will be a major shift in the
structure of industry as industrialized societies evolve into information societies. Basedon the successful application of materials
design to the development of new spin control methods for semiconductor spintronics
and new valence electron control methods
known as simultaneous codoping in wideband-gap semiconductors, it is expected thatab initio calculation will prove to be a powerful tool with considerable future potential.
Keywords: ab initio calculation, materials design, codoping, semiconductor spintronics, wideband-gap semiconductors, valence control, magnetic semiconductors, Spin-FET, Spintransistor

1. Materials Design and Industrial Structure Change
In the electronics industry, devices areproduced based on materials, and softwareis then developed to run on these devices.
This corresponds to a three-layer hierarchical structure (materials → devices → software). As industrialized societies evolve into
information societies in the 21st century, industries will shift the emphasis of their workfrom materials to devices, and from devices
to software. To develop software based on
new concepts, new devices must be made to
implement these concepts, and new materials that possess new functions are needed forthe fabrication of these new devices. Con-

versely, the discovery of new materials withnew functions has a far-reaching impact not
only on science and technology but also on
economics and culture, and thus even in the
21st century the efficient research and development of materials with new functions will
greatly influence the future of humanity. For
the efficient discovery and development ofadvanced materials with novel properties, it
is essential to design materials based on new
theoretical procedures without relying solely
on experiment instead of adopting the trialand-error approach to development that hashitherto been the mainstream.
In recent years, great advances havebeen made in computers and computational
physics procedures, and by performing ab initio calculations based on quantum mechanics(the basic laws at the quantum level of matter), it has become possible to quantitatively
predict the physical properties of diverse systems with only atomic numbers as the input
parameters. Compared with conventional
theory based on simple models whose parameters have to be determined experimentally, ab initio calculation is perhaps the only
theoretical framework that can quantitatively
predict electronic states and physical properties for virtual materials and new materials
that do not yet exist in the real world. Therefore, ab initio calculation is called as “thestandard model of the condensed matters”.
Previous papers have already discussed thefeasibility and practicality of materials design
based on the prediction of physical properties by ab initio calculation.1-5) Osaka University is at the forefront of this work, where
this grand challenge is being met by combining novel ideas with the prediction of physical properties by ab initio calculation. Spe-

* The Institute of Scientific and Industrial Research, Osaka University (8-1 Mihogaoka, Ibaraki 567-0047).
** Kochi University of Technology (185 Miyanoguchi, Tosayamada-cho, Kochi 782-8502).

20

JSAP International No.6 (July 2002)

cifically, these research on materials design isbeing carried out at the Institute of Scientificand Industrial Research by Hiroshi KatayamaYoshida, Hisatomo Harima and Koun Shirai,
at the Graduate School of Science by scientific researchers Hisazumi Akai and Takeo Kotani, and at the Graduate School of Engineering Science by Masafumi Shirai and Naoshi
Suzuki. This research is recognized all over
the world as originating from Osaka, andthe computational physics software for materials design that was developed here withthe assistance of public finance has been
made publicly available and is provided freeof charge to many researchers and technologists.6-8)
To clarify the great usefulness and future prospects of this research, this paper
describes how ab initio calculation is used in
the design of new valence electron control
methods and new spin control methods forsemiconductor spintronics, and compares thepredictions with experimental results.

2. The Design of Valence Electron Control Methods for
Wide Bnad-Gap Semiconductors
Wurtzite ZnO (Eg = 3.3 eV) and GaN (Eg= 3.4 eV) have a direct transition band gap(Eg) and are transparent to visible light. Since
these materials contain N and O, which arehighly electronegative, they are readily dopedwith electrons, but are very difficult to dopewith holes. This property is known as unipolarity. Due to the electronic excitation thatarises from the shift of the Fermi level corresponding to Eg due to doping with a highdensity of holes, the acceptor atoms leaveatomic vacancies behind and undergo atomic

traction between acceptors
use exciton light-emission mechanisms. In(A) and donors (D) to form apractice, polycrystalline ZnO has been shown
meta-stable
A-D-A
complexto undergo CW laser action under optical��������
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which
is
frozeninthethinexcitation. 10) To examine ways of produc��������
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film crystal. Using atomic
ing low-resistance p-type ZnO, we have per���
layer epitaxial growth, it isformed ab initio materials design calculations
���
possible to form an A-D-A
to study the effects of codoping ZnO with���complex alternately doped
Ga, Al and In donors and N acceptors.9-11)�������������
���with A and D in atomic layer
Codoping ZnO with Ga donors and N ac��������
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epitaxy (ALE). The formation
ceptors in a 1:2 ratio results in a metastable���
of an A-D-A complex results
N-Ga-N complex in the ZnO. When doped���in strong ionic properties, so
only with N, the wave function of the accepthat the Madelung energy
tors is strongly localized at the positions of���is reduced. And since thethe N atoms and a deep acceptor level (300�������������
���
latticeisrelaxedbydopingmeV) is formed, but when an N-Ga-N com�����������
with two types of atom havplex is formed, the strong hybridization be���
ing different ionic radii, thetween the N and Ga wave functions causes���solubility greatly increases
the N acceptor levels to shift toward lower���under thermal non-equilibenergies and the wave function spreads out.
�������������
���rium conditions. Codoping
The impurity band is also made wider due to��������
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also has the effect of screenthe presence of the N acceptors, and the ef���
ing the impurity potential
fective mass of the acceptors becomes small���and changing the scatterer (see Fig. 1). When doped only with Ga,
ing mechanism from a longthe Madelung energy decreases, and with N
���
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range Coulomb scattering
it increases, giving rise to unipolarity. On the�����������
mechanism to a short-range
other hand, the N-Ga-N complex formed bymultipole scattering mechacodoping has a much smaller Madelung enFig. 1: Local density of states in ZnO (a) when doped only with N, andwhen codoped with N acceptors and (b) Al, (c) Ga or (d) In donors (1:2). As
nism, and thus lead to subergy (see Table 1) and can thus be doped
the dotted lines show, codoping has the effect of shifting the N impurity
stantially increased mobility.
with a high density of N acceptors.11)
band toward lower energies. This band also becomes broader, and the effective mass decreases.9)
Due to the structure of theBased on our materials design method,
A-D-A complex, the wave
Tabata, Kawai et al. have successfully protransfer to interstitial sites. This gives rise to afunctions of the acceptors and donors are
duced low-resistance p-type ZnO with a carricompensatory effect whereby acceptors turnstrongly hybridized, causing the acceptor
er density of 4 1019 cm-3 and a resistivity of
into donors. To prevent this, it is necessary tolevels (bonding states) to shift toward lower
2 Ω·cm by laser MBE with ECR-excited N2O
use a doping method that increases the soluenergies while the donor levels (antibonding
and Ga2O3 as the codoping sources. 12) The
bility of acceptor atoms by stabilizing themstates) shift toward higher energies. As a relow-resistance p-type and n-type ZnO proat substitution sites. Also, a wide band-gap
sult, the acceptor levels
semiconductor generally has a small dielectric
become to be shallowconstant; in ZnO:N (300 meV) and GaN:Mg
er, and the activation
Table 1 The change in Madelung energy (relative to non-doped ZnO) when
doping with pure donors and acceptors, and when codoping with donors(200 meV) the acceptor level is very deep,
rate of the carriers isand acceptors.
and at room temperature (≈30 meV) the actigreatly increased.
vation rate is extremely low. To achieve lowZnO is very enviChange in Madelung
er resistance it is necessary to use a doping
ronmentally friendly
Doping typeenergy relative tomethod in which the acceptor level itself ismaterial whose excinon-doped ZnO (eV)made shallower.
ton bound energy of
ZnO: Al-6.44
To solve these problems at a stroke, we
60 meV is greater thanZnO: Ga-13.72have developed a valence electron control
that of GaN (24 meV)��������������������������������

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method called codoping based on ab initio
calculation, and we have applied it to numerous systems.9,11-22) Codoping involves using
non-equilibrium crystal growth technique
at a low temperature where diffusion is restricted to simultaneously dope the crystal
with donors and acceptors in a 1:2 density
ratio. This technique exploits the electrostatic
repulsion between acceptors (A) and the at-and allows excitons
to exist stably even atroom temperature. It istherefore also a promising material for use inlight-emitting devices
and next-generation
short-wavelength semiconductor lasers that

ZnO: In-9.73

ZnO: N+0.79

ZnO: 2N+0.91

ZnO: [Al+2N]-4.74

ZnO: [Ga+2N]-12.06

ZnO: [In+2N]-7.79

JSAP International No.6 (July 2002)

21

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Fig. 3: Total energy difference between the ferromagnetic state and the antoferromagnetic spinglass state in GaAs, GaN, ZnO and ZnTe containing a solid solution of 5-25% transition metal ions.

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Fig. 2: Density of states in GaN.14)(a) Non-doped GaN, in which
there are no doped holes. (b)GaN codoped with O donors andMg acceptors in the ratio 1:2. (c)GaN codoped with Si donors andMg acceptors in the ratio 1:2.

duced by codoping is transparent to visible
light and electrically conductive, and is thus
ideal for the electrodes of efficient solar cells
and for transparent electronic devices. Thesematerials also have important potential applications in ultraviolet light-emitting devices
and short-wavelength optoelectronic devices
with p-n junctions.12)
We have also managed to stabilize highdensities of acceptors in GaN by codopingwith Mg and Be acceptors and Si and O donors to produce the complexes Mg-Si-Mg,
Mg-O-Mg, Be-Si-Be and Be-O-Be, and wehave designed materials in which the formation of these A-D-A complexes makes theacceptor levels shallower, resulting in p-typesemiconductors with lower resistance (Fig.
2).14-22) Compared with single doping, codoping increases the number of carriers and theelectrical conductivity by approximately twoorders of magnitude.15)
Many of the predicted effects of codoping13-22) have subsequently been verified ex-

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perimentally. Ploog et al. experimentally verified the codoping of GaN:(2Be+O).23) When
doping GaN with Be acceptors, they discovered by chance that it can be made p-type
simply by performing MBE with the additionof O donors. Subsequent secondary ion mass
spectroscopy (SIMS) experiments showedthat the Be and O had been codoped withhigh densities (Be = 2 1021 cm-3, O = 1
1021 cm-3), and as a result the carrier density(5 1018 cm-3) and mobility (150 cm2/Vs) increased, causing the semiconductor to turninto a low-resistance p-type (resistivity 0.02Ω·cm). Recently, they have also made lowresistance p-type materials by codoping with
controlled quantities of Be and H2O.23)
The fact that low-resistance p-type semiconductors can be produced by codoping is
also clear from the results of SIMS measurements of commercial high-brightness whiteLEDs with the structure /AlGaN (n-type: Eg =3.6 eV)/InGaN (MQW: Eg = 3.2 eV)/AlGaN (ptype: Eg = 4.1 eV)/, where the p-type regions

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are found to be doped with O and Mg densities of a similar order (O ≈ 1020 cm-3; Mg ≈2 1020 cm-3). A patent application in which
the density of Mg acceptors is increased byapproximately two orders of magnitude bycodoping with Si or O donors to reduce theresistivity by approximately two orders ofmagnitude was submitted by Nichia Corporation24,25) 1-2 months after our own patent application.15)
Recently, Wessels et al. used MOCVD toperform systematic tests of codoping with
Mg acceptors and O donors, and reported
that the resistivity decreases from 8 Ω·cm bya factor of approximately 40 while the acceptor levels drop to 135 meV and the p-typecarrier density and mobility increase by atleast an order of magnitude.26) According toour materials design method, codoping with
2Mg+O increases the p-type carrier density
to 8 1020 cm-3 and reduces the resistivity toless than 0.01 Ω·cm.15)
Codoping is a generally applicable tech-�������

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Fig. 4: The density of states produced when a transition metal (V, Cr, Mn, Fe, Co, Ni) is incorporated as a 25% solid solution in ZnO in a ferromagnetic state. Red lines show the total density of states per unit cell, and blue lines show thepartial density of states for each atom with a 3d orbital. The d band, which exhibits prominent exchange splitting, occupies an increasingly large proportion as the atomic number of the transition metal impurity increases, and thus thetransition metal ions are in high spin states. For Mn it can be seen that this corresponds to d5.

nique, and is widely applied to cases where
it is difficult to control valence electrons inthermal equilibrium conditions or conventional crystalline deposition,17,30) such as lowresistance p-type CuInS 2 :(V Cu +In Cu +2P), 22)
low-resistance p-type ZnSe:(2N+In),22) low-resistance p-type AlN:(2C+O),27) low-resistancep-type GaN:(2C+O), low-resistance p-type
SrTiO3:(2N+Nb)28) and low-resistance n-type
diamond:(2P+H, 2N+B, H+S). 29) A background of the designs relating to codoping
and more elaborate descriptions of codoping in materials such as GaN and ZnO can befound in the references.31)

3. Design of Spin Control
Methods for Transparent Ferromagnetic Semiconductors
Electrons in a semiconductor have twodegrees of freedom: charge and spin. In
the conventional electronics, the charge
is controlled in the semiconductor devices
in the valence and conduction electrons.
Semiconductor spintronics (spin electronics) is a new branch of electronics in which
the spin degree of the freedom is also controlled. The interaction between localized
spin states doped into a semiconductor depends on (1) the density N and type (p-type
or n-type) of carriers upon doping, (2) the
scale size (L) which is correlated to the spin
coherent length, and (3) the dimensionalityof the semiconductor structure (d = 0, 1, 2,3) fabricated by nanotechnology. It is possible to control these spin states in any way
one likes by means of subminiature processing and charge control, which are both readily achieved in semiconductor materials. Here,with regard to the interaction between spinstates in semiconductors, we will use ab initio
calculation to predict the spin state interactions in different host semiconductor materials (the group II-VI semiconductors ZnO, ZnS,
ZnSe and ZnTe, and the group III-V semiconductors GaAs and GaN), and their dependence on the type and doping density oftransition metals (V, Cr, Mn, Fe, Co, Ni) andthe type (p-type or n-type) and density of carriers in these materials. Figure 3 shows theresults obtained by using the KKR-CPA method to calculate the total energy difference
between the ferromagnetic state and the

JSAP International No.6 (July 2002)

23

antiferromagnetic spin glass state in GaAs,
GaN, ZnO and ZnTe including a 5-25% solid
solution of transition metal ions.32) Due tolack of space, the results for ZnS and ZnSe
are omitted.
In group II-VI semiconductors, V and
Cr all form ferromagnetic half-metal states(where a spin in one direction has a metallic state and a spin in the opposite direction
has an insulating state), and it is possible toproduce and extract 100% spin-polarized
electrons from the Fermi surface (see Fig.
4).32) With V and Cr, the Fermi level is situated at the t2 state, which is the strong antibonding state of p-d hybridization (between
the transition metal’s 3dε orbital (d(xy), d(yz),d(zx)) and the p orbital of the host material (px, py, pz)), This p-d hybridization causes
the band energy to decrease by allowing 3dholes with spin-up states (majority spin) to
migrate through the crystal, and stabilizes�����������������������������

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the ferromagnetic half-metal state because
the ferromagnetic double exchange interaction overcomes the antiferromagnetic superexchange interaction. This mechanism for the
expression of magnetism has already been
proposed and discussed by Akai for the caseof (In, Mn)As.35) From the viewpoint of materials design, strong ferromagnetism can be
expected from V and Cr in group II-VI semiconductors.
When Mn is present in a group II-VI
semiconductor, the Zn2+ is substituted with
Mn2+ (d5) to form an insulator, the carriers
are not doped, and the antiferromagnetic
superexchange interaction predominates sothat the ground state is an insulating antiferromagnetic spin glass. If holes are doped
into these systems by N acceptors, most of
the holes enter t2 states with strong p-d hybridization, the Mn2+ (d5) changes into Mn3+(d4), the 3d holes in up spin states migrate����������������
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Fig. 5: The dependence of the total energy difference between the ferromagnetic state andantiferromagnetic spin glass state on the hole and electron densities in solid solutions of 5-25%transition metal ions (Mn, Co) in ZnO.

24

JSAP International No.6 (July 2002)

through the crystal via the strong p-d hybridization, and the ferromagnetic double
exchange interactions become predominantresulting in a ferromagnetic half-metal state(Fig. 4).34) The possibility that ZnO or GaN
that has been doped with a high density of
Mn and holes may have a high Curie temperature (Tc) has also been discussed in termsof the mean field approximation due to p-dinteractions.35) On the other hand, in the caseof electron doping with a Ga donor (Mn2+ +electrons), the electron states in the vicinityof the Fermi level for down-spin states are located at the bottom of the conduction band.
These states includes almost no Mn 3d components, and since the doped electrons enter
the Zn 4s orbitals (which are in the conduction band of the ZnO host material), the 3delectrons are unable to migrate and remain
as Mn2+ (d5) so that the antiferromagnetic
superexchange interaction predominates
and the antiferromagnetic spin glass state ismaintained34) (Figs. 4, 5).
For Fe, Co and Ni in ZnS, ZnSe and ZnTe,
the Fermi level is situated at the localized estates (in the band gap) where the p-d hybridization (between 3d γ orbitals and p orbitals) is weak. This results in weak migration
properties, and thus the antiferromagnetic
superexchange interaction predominates
and an antiferromagnetic spin glass stateis achieved. On the other hand, for Fe, Co
and Ni in ZnO, exchange splitting causes thedown-spin states to enter the conduction
band. As a result, the 3d electrons migrate
through the crystal due to the s-d hybridization between the conduction band (Zn 4s)
and 3d orbitals (e states), and the ferromagnetic double exchange interaction predominates so that the ferromagnetic half-metalstate assumes the ground state34) (Fig. 4). In
ZnO, since it is very easy in practice to produce a low-resistance n-type semiconductor
by doping with a donor such as Ga, Al or In,
it is possible to achieve a stable transparent
ferromagnetic state with a high Tc by electron
doping with Fe, Co or Ni (Fig. 5).34) When V,
Cr, Mn + holes, Fe, Co or Ni is doped into
ZnO, exchange splitting outweighs crystal
field splitting, resulting in a high spin state
and a large saturated magnetic moment. 34)
Such systems absorb long infrared light, but

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Fig. 6: The density of states obtained by forming a 5% solid solution of transition metal
ions (Cr, Mn, Co) in GaN in a ferromagnetic state. Red lines show the total density ofstates per unit cell, and blue lines show the partial density of states for each atom witha 3d orbital. In the case of Cr and Mn, the Fermi level is situated in a band originatingfrom spin-up t2 states, whereas in the case of Co the Fermi level is situated in a band ofdown-spin e states.

in the visible light region they hardly absorb
any light except for absorption by the excitation of inner-shell 3d orbitals in the transition
metal, resulting in a transparent ferromagnetic material. For example, Co produces askeleton transparent ferromagnetic semiconductor material with a cobalt blue color.
Doping GaN or GaAs with V, Cr or Mn
has the effect of introducing holes into thesemiconductor. Spin-up 3d holes that areclose to the Fermi level mainly enter a t2 statewith strong p-d hybridization (between 3d
ε orbitals and p orbitals), which allows themto migrate through the crystal, resulting in aferromagnetic half-metal state due to the socalled double-exchange interaction arisingfrom the reduction of band energy. In particular, the most stable ferromagnetic states
are achieved with V and Cr36,37) (see Figs. 3,
6 and 7). When GaN is doped with Mn, theMn exhibits ferromagnetism when it is dopedwith a low concentration and occupies few

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Fig. 7: The density of states obtained by forming a 5% solid solution of transition metal
ions (Cr, Mn, Co) in GaAs in a ferromagnetic state. Red lines show the total density ofstates per unit cell, and blue lines show the partial density of states for each atom witha 3d orbital. In the case of Cr and Mn, the Fermi level is situated in a band originatingfrom spin-up t2 states, whereas in the case of Co the Fermi level is situated in a band ofdown-spin e states.

sites. But as its concentration increases, thenumber of antiferromagnetic superexchangeinteractions between closest-neighbor MnN-Mn atoms increases, causing it to switchfrom the ferromagnetic state into an antiferromagnetic spin glass state36) (see Fig. 3). If
the holes are compensated by doping thesesystems with the O donors, the antiferromagnetic spin glass state becomes more stable.30)
When Fe3+ (d5) is doped into GaN or GaAs,
the carriers are undoped and the antiferromagnetic spin glass becomes stable due tothe antiferromagnetic superexchange interaction. Doping Co and Ni into GaAs and GaN
causes the states close to the Fermi level tohave opposite spins, weakening the p-d hybridization (between the 3d γ orbitals [d(3z222 2γ ), d(x -y )] and p orbitals [p x, py, pz]) andcausing localized e states to appear in theband gap. This weakens the migration properties and allows the antiferromagnetic superexchange interaction to predominate overthe ferromagnetic double exchange interaction, resulting in an antiferromagnetic spinglass state.37)
These results correspond well with theresults of experimental measurements. For
example, recent measurements of opticaltransmittance in ZnO doped with transition
metals synthesized by laser MBE have shownthat it forms a transparent material. 38) ZnO
doped with 15% Co exhibits ferromagnetism
above room temperature (Curie temperature
Tc = 280 K),38) while Ni-doped ZnO is ferromagnetic at low temperature and super paramagnetic at room temperature, and the existence of ferromagnetic interaction has been
observed.30) For the (Ga,Mn)As system, experiments conducted before the materials design have shown that it forms a ferromagnetic material with a Tc of about 100 K, which
agrees well with the calculated results.40) Experiments have also been performed recently
with (Ga,Cr)As, Yoshino et al. have reported

JSAP International No.6 (July 2002)

25

that it exhibits ferromagnetism.41) Shirai42) has

Si, Ge, perovskite SrTiO3,45) chalcopyrite-type

and electrons can be guided to the paramag-

used a full-potential linearized augmentedplane-wave (FLAPW) super-cell method to

CuGeP2, CuAlS2, TiO2 and SiO2.
Some possible device applications of thisnetic region, and if this can be done in sufficient quantities to produce a ferromagnetic

design (Ga,Cr)As and CrAs materials with azinc-blende structure that exhibit ferromagnetism, and a zinc-blende type ferromagnetic

technology are as follows. A crystalline mixture of Mn (antiferromagnetic) and Fe (ferromagnetic) in ZnO (ZnO:FexMn1-x) or of Cr

half-metal state by optical excitation, thenthis structure can be made magnetic simply by shining light onto it. It is also possible

CrAs half metal with a Tc of over 400 K wasrecently synthesized by Akinaga et al.43) There(ferromagnetic) and Mn (antiferromagnetic)
in ZnO (ZnO:CrxMn1-x) can be produced so as

to fabricate transistors from Mn-doped ZnO(ZnO:Mn). Although this is an antiferromag-

are other systems apart from these on which
no experiments have been performed so far,to keep the material in a paramagnetic stateon the threshold of ferromagnetism. This

netic material, it can be changed from anantiferromagnetic insulator into a ferromag-

so further experimental investigations are
expected. Materials design methods of thismixture is deposited on a substrate such as
GaAs or Si. Since it is transparent, it allows

netic half-metal state by using semiconductor superstructure techniques to fabricate asort have recently been extended to the design of other materials such as group III-V/II-

visible light to pass through and strike thesubstrate, where it stimulates electrons and/metal/insulator/semiconductor/ superstructure consisting of /p-type ZnO/insulating ZnO/

VI superlattice magnetic semiconductors,44)

holes. By applying a bias voltage, the holes

ZnO:Mn/ and doping the ZnO:Mn layer with

(8) KKR-CPA (Coherent Potential Approximation) Method Program (MACHIKANEYAMA-2000) is developed by Prof. H. Akai
[akai@phys.sci.osaka-u.ac.jp], Department of Physics, Osaka University, Osaka
560-0043, Japan. MACHIKANEYAMA-2000
is one of the free packages opened for the
public use by OUFP-CMD (Osaka University
Free Package for Computational Materials
Design).
(9) T. Yamamoto and H. Katayama-Yoshida :Jpn. J. Appl. Phys. 38, L166 (1999).
(10) A. Ohtomo et al. : J. Mater. Sci. Eng. B inpress. Y. Segawa et al. : Phys. Status Solidi b
202, 669 (1997).
(11) H. Katayama-Yoshida and T. Yamamoto,
Fabrication Method of the Low resistive
p-type ZnO, Japanese Patent Application,(JPH10-287966).
(12) M. Joseph, H. Tabata and T. Kawai : Jpn. J.
Appl. Phys. 38, L1205 (1999). X.-L. Guo, J.-H.
Choi, H. Tabata and T. Kawai : Jpn. J. Appl.
Phys. 40, L177 (2001).
(13) T. Yamamoto and H. Katayama-Yoshida :Inst. Phys. Conf. Ser. 152, 37 (1998).
(14) T. Yamamoto and H. Katayama-Yoshida :Jpn. J. Appl. Phys. 36, L180 (1997).
(15) H. Katayama-Yoshida, Fabrication of the
Low-resistive p-type GaN, Japanese Patent,(Japanese Patent Number 322329).
(16) T. Yamamoto and H. Katayama-Yoshida :Gallium Nitride and Related Materials, Vol.
46, ed. C. R. Abernathy, H. Amano and J. C.
Zolper, p. 105 (Materials Research Society,
Pittsburgh, 1997).
(17) T. Yamamoto, and H. Katayama-Yoshida,
Solid State Physics, 32, 59 (1997).
(18) T. Yamamoto and H. Katayama-Yoshida : J.
Cryst. Growth 189/190, 532 (1998).

(19) H. Katayama-Yoshida, T. Yamamoto and T.
Nishimatsu : Phys. Status Solidi b 210, 429(1998).
(20) H. Katayama-Yoshida and T. Yamamoto :Proc. Int. Conf. Solid State Devices and Materials, p. 62 (1997).
(21) H. Katayama-Yoshida, T. Yamamoto andT. Nishimatsu : Compound Semiconductors
1998, ed. H. Sakaki, J.-C. Woo, N. Yokoyama
and H. Hirayama, Inst. Phys. Conf. Ser. No.
162, p. 747 (IOP Publishing, London, 1999).
(22) H. Katayama-Yoshida and T. Yamamoto :Phys. Status Solidi b 202, 763 (1997).
(23) O. Brandt, H. Yang, H. Kostial and K. H. Ploog : Appl. Phys. Lett. 69, 2707 (1996). K. H.
Ploog and O. Brandt : J. Vac. Sci. & Technol.
A 16, 1609 (1998).
(24) S. Nakamura et. al. Crystal Growth Methodof p-type Nitride Semiconductor and Nitride
Semiconductor Devices, Japanese Patent Application, (JPH10-154829).
(25) S. Nakamura et. al. Fabrication of p-type Nitride Semiconductor and Nitride Semiconductor Devices, Japanese Patent Application,(JPH10-144960).
(26) R. Y. Korotokov, J. M. Gregie and B. W. Wessels : Appl. Phys. Lett. 78, 222 (2001).
(27) T. Yamamoto and H. Katayama-Yoshida:
Physica B, 273/274, 113 (1999).; H. Katayama-Yoshida, United State Patent, (USP
6281099); European Union Patent, (Patent
Number, EP-1037268A1); Japanese Patent
Application, (JP2000-31059): Method forSynthesizing Single Crystal AlN Thin Films of
Low Resistance with n-type and p-type.
(28) K. Betsuyaku and H. Katayama-Yoshida, Jpn.
J. Appl. Phys. 40, 6911 (2001). ; H. Katayama-Yoshida, K. Betsuyaku et al., Fabricationof Low-resistive p-type SrTiO3, Japanese Patent Application, (JPH12-087069).

References(1) H. Katayama-Yoshida, and K. Terakura, Electronic Structure Calculation and Materials
Design System, Solid State Physics, Special
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(2) H. Katayama-Yoshida, Towards the Materials
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(6) F L A P W M e t h o d P r o g r a m ( K A N SAI-94) is developed by Prof. H. Harima[harima@sanken.osaka-u.ac.jp], The Institute of Scientific and Industrial Research(ISIR), Osaka University, Osaka 567-0047, Japan. KANSAI-94 is one of the free packages
opened for the public use by OUFP-CMD(Osaka University Free Package for Computational Materials Design).
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by OUFP-CMD (Osaka University Free Package for Computational Materials Design).

26

JSAP International No.6 (July 2002)

holes by applying a bias voltage. This allows

ity depends strongly on whether or not it istron-stimulated atomic manipulation. Thisa 100% spin-polarized current to flow, and it

possible to efficiently develop highly efficientstudy was also greatly assisted by financial

is thus possible to make spin-FETs and spintransistors.46) It seems likely that semiconductor spintronics devices of this sort will soonenergy conversion materials, environmentally
harmonious materials, and materials for medical care applications. Ab initio materials de-and technical assistance provided by otherorganizations such as the Center of Excellence (COE) at Osaka University, Institute of

be realized.

sign is likely to play an important role in thiseffort. So when taxpayers ask us why we are

Scientific and Industrial Research, ACT-JST
project by the Japan Science and Technology

4. Conclusion
In the 21st century, the most important

studying ab initio materials design, we tellthem it is for the distant future of humanity.

Corporation (JST), the Future Grogram of theJapan Society for the Promotion of Scienceproblems that need to be addressed on aworldwide scale are the energy problems,

Parts of this study were funded by the
Ministry of Education, Culture, Sports, Sci-

(JSPS), and the Nano-Tech Materials by New
Energy and Industrial Technology Develop-

environmental problems, and the problemsof addressing the medical needs of an aging

ence and Technology with a grant-in-aid forscientific research of priority areas: (A) spin

ment Organization (NEDO), and all of theseresearch are dedicated to the distant futuresociety. Materials design can help to solvethese problems, and the future of human-

control semiconductors nanostructurs and(A) molecular physical chemistry, and (B) elec-of humanity.
Onward and upward

Note added in proof(29) T. Nishimatsu, H. Katayama-Yoshida, and N.
Orita, Jpn. J. Appl. Phys. 41, 1952 (2002).;
H. Katayama-Yoshida, United State Patent (USP 6340393), European Union Patent,(EP1036863A1), PCT International Patent Application, (WO00/01/01867), Japanese Patent
Application (JP2000-26194), (JPH10-208611),(JPH10-247624), (JPH9-50106): Method forSynthesizing n-type Diamond Having Low Resistance.
(30) New Valence Control and Spin Control
Method of Codoping in a Thermal Nonequilibrium Crystal Growth, H. KatayamaYoshida, K. Sato, R. Kato, and T. Yamamoto,
Journal of the Japanese Association for Crystal Growth, 27,232 (2000). ; H. KatayamaYoshida, R. Kato and T. Yamamoto: J. Crystal
Growth, 231, 428 (2001).
(31) T. Yamamoto, New Diamond 17, 18 (2001);
NEDO Research Report (2001) p.43.
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Appl Phys. 40, L651 (2001).; H. KatayamaYoshida, and K. Sato, Fabrication of Ferromagnetic II-VI (ZnTe, ZnSe, ZnS, CdTe, CdSe,
CdS) based Transition Metal Doped Magnetic
Semiconductors and Control Method of Ferromagnetism, Japanese Patent Application,(JP2001-059164).
(33) H. Akai : Phys. Rev. Lett. 81, 3002 (1998).
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Appl. Phys. 39, 555 (2000); ibid 40, L334
(2001); H. Katayama-Yoshida, and K. Sato,
Fabrication of Ferromagnetic ZnO based
Transition Metal Doped Magnetic Semiconductors and Control Method of Ferromagnetism, Japanese Patent Application,(JPH11-247959), (JPH11-308911).
(35) T. Dietl, et al. : Science 287, 1019 (2000).
(36) K. Sato and H. Katayama-Yoshida : Jpn. J.
Appl. Phys. 40, L485 (2001).

(37) K. Sato and H. Katayama-Yoshida, Semicond. Sci. Technol. 17, 367 (2002)., and unpublished results; H. Katayama-Yoshida, and
K. Sato, Fabrication of Ferromagnetic III-V
Nitride (GaN, AlN, InN, BN)based Transition
Metal Doped Magnetic Semiconductors andControl Method of Ferromagnetism, Japanese Patent Application, (JP2001-059303).;
H. Katayama-Yoshida and K. Sato, Fabrication of Ferromagnetic III-V (GaAs, InAs, GaP,
InP) based Transition Metal Doped Magnetic
Semiconductors and Control Method of Ferromagnetism, Japanese Patent Application,(JP2001-059195).
(38) K. Ueda, H. Tabata, and T. Kawai: submitted
to Appl. Phys. Lett., 79, 988 (2001).
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Abe, A. Ashida and T. Ito : Physica E 10, 260(2001).
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(1998).
(43) H. Akinaga, T. Manago and M. Shirai : Jpn. J.
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Added note (1): Complex nature of very shallow acceptor levels of 14 meV from the valenceband maximum in Mg doped p-type Al0.2Ga0.8N(band-gap energy is 4.1 eV) is observed and its
acceptor is activated even at 100K. [Y. Zohta, Y.
Iwasaki, S. Nakamura, and T. Mukai, Jpn. J. Appl.
Phys. 40, L423 (2001).]. See the discussion of thecodoping (O+2Mg, Si+2Mg) for the fabricationof the low-resistive p-type GaN in the recent review paper [H. Katayama-Yoshida, T. Nishimatsu,
T. Yamamoto, and N. Orita, J. Physics. Condens.
Matter. 13, 8901 (2001)].
Added note (2): Room temperature ferromagnetism in Mn doped GaN (Curie temperature
Tc ~ 940K), [S. Sonoda, S. Shimizu, T. Sasaki, Y.
Yamamoto, and H. Hori, J. Crystal Growth, inpress], and Cr doped GaN (Tc > 400K) [M. Hashimoto, Y-K. Zhou, M. Kanamura, and H. Asahi,
Solid State Commun. 122, 37 (2002).] are fabricated based upon the materials design. However,the predicted Tc from the ab initio calculation is
Ga0.95Mn0.05N (Tc=350K), Ga0.95Cr0.05N (Tc=500K),
Ga 0.95Mn 0.05 As (Tc=260K), and Ga 0.95 Cr 0.05 As(Tc=520K), [K. Sato, P. H. Dederichs, and H. Katayama-Yoshida, to be published.].
Added note (3): Higher Tc (Tc ~ 15K) in Cr
doped ZnTe is reported [H. Saito, W. Zaets, S.
Yamagata, Y. Suzuki, and K. Ando, J. Appl. Phys.
91, 8085 (2002).]. However, the predicted Tc
from the ab initio calculation is Zn 0.95Cr 0.05Te(Tc=350K), Zn0.95Cr0.05Se (Tc=300K), Zn0.95V0.05Te(Tc=200K), and Zn0.95V0.05Se (Tc=400K), [K. Sato,P. H. Dederichs, H. Katayama-Yoshida, to be published.].
Added note (4): Higher Tc (Tc > 350K) in V
doped n-type ZnO is reported [H. saeki, H. Tabata and T. Kawai, Solid State Commun. 120,
439 (2001)]. However, the predicted Tc from theab initio calculation is Zn0.85V0.15O (Tc=480K), [K.
Sato, P. H. Dederichs, H. Katayama-Yoshida, to be
published.].

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