bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mapping of Defects in Metal-Semiconductor-Metal (MSM) Detectors in Hg1−xCdxTe by Nuclear Microprobe
Authors: Leech Patrick W. , Dooley Sean P. , Jamieson David N. 
Published: April 2011

AbstractThe incidence of compositional and structural inhomogenieties in MSM detectors based on Hg1−xCdxTe/GaAs and Hg1−xCdxTe/GaAs/Si has been examined by nuclear microprobe. With a 2 MeV He+ beam focussed to ≤5 μm, the microprobe has demonstrated the capability for RBS channelling in the active region of a Hg1−xCdxTe device and the imaging of defects by Channelling Contrast Microscopy (CCM). A series of linear growth defects in some Hg1−xCdxTe devices were identified using CCM. The channelling RBS spectra from these regions have shown an increase in χmin compared with the surrounding high quality crystal. The occurence of these defects was associated with a degradation in the performance of affected devices in an array. RBS spectra have also revealed the presence of an anomalous CdTe layer, correlating with a significant reduction in dark current and increase in breakdown voltage of these devices. RBS channelling of individual devices has identified differences in χmin between arrays which were prepared under equivalent conditions of growth and processing.
HgCdTe MBE Technology: A Focus on Chemical Doping
Authors: Wu Owen K. 
Published: April 2011

AbstractHgCdTe MBE technology is becoming a mature growth technology for infrared focal plane array applications. The ability to dope HgCdTe with In(n-type) and As(p-type) dopants in-situ provides greater flexibilities for fabricating heterojunction devices. In this paper, we will first discuss the current status of HgCdTe MBE growth and then focus on the key results in the control of In(n-type) doping, various approaches and breakthroughs in the growth of As(p-type) doped HgCdTe and issues related to doping such as memory effects and dopants activation. In addition, device results from double layer heterojunction structure(DLHJ) will be briefly discussed.
IV-VI on Fluoride/Si Structures for IR-Sensor Array Applications
Authors: Fach A. , Maissen C. , Masek J. , Teodoropol S. , Zogg H. 
Published: April 2011

AbstractEpitaxial narrow gap IV-VI layers on Si-substrates offer an alternate to Hg1−xCdxTe for IR-focal plane arrays with similar ultimate sensitivities. We report on the following improvements in reaching the goal of an easily producible fully monolithic IV-VI-on-active-Si IRFPA: (1) Up to now, compatibility with the Si-substrate was reached through use of a stacked CaF2/BaF2 buffer layer. This layer is replaced by a very thin CaF2 buffer only, which is more suitable for photolithographic processing. (2) Fine resolution wet etching of the IV-VI layers is much easier and reproducible with this new type of buffer. (3) Good homogeneity of cut-off wavelengths is obtained: For a 12 mm long linear Pb1−xSnxSe array with 10.2 μm cut-off wavelength at 95K, the variation in cut-off is smaller than 0.1 μm. (4) The thermal mismatch strain relaxes by dislocation glide even at cryogenic temperatures and after many thermal cycles.
High-Performance Lead Telluride-Based Photodetectors
Authors: Akimov Boris A. , Khokhlov Dmitriy R. 
Published: April 2011

AbstractWe present the new class of the far infrared photodetectors based on the lead-tin tellurides doped with the group III impurities. The persistent photoconductivity effect appearing in these materials provides an internal signal integration resulting in a considerable increase in the signal-to-noise ratio. The techniques of the photomemory quenching are discussed. In some regime of quenching the effect of giant quantum efficiency stimulation has been observed. The possibility of generation of the photoinduced spatially nonequilibrium states provides the physical evidence for the construction of an integrating “continuous” focal-plane array based on Pb1−xSnxTe(In).
Effect of Solutal Convection During the Growth of Silicon in a Sandwich System
Authors: Dost Sadik , Djilali Ned , Erbay Saadet , Erbay Husnu A. 
Published: April 2011

AbstractThis paper considers the modelling of Liquid Phase Epitaxial (LPE) growth of silicon in a substrate-solution-substrate “sandwich” system. Unsteady two-dimensional numerical simulations which take into account fluid flow and mass transfer are presented for a growth experiment. Except in the initial stages, solutal convection is found to be dominant throughout the process. Convection is, however, mostly confined to the upper half of the growth cell, resulting in growth of a layer on the upper substrate, which is about twice as thick as that on the lower substrate. This result is in good agreement with available experiment data. Another interesting consequence of the convection patterns is the formation of a smooth flat surface on the lower substrate and a wavy irregular one on the upper substrate.
A Long-Wavelength Infrared Photoluminescence Spectrometer for the Characterization of Semiconductor Materials
Authors: Wright R. P. , Kohn S. E. , Haegel N. M. 
Published: April 2011

AbstractA new photoluminescence spectrometer has been developed for the characterization of optical emission in the 2.5 to 14.1 micron wavelength range. This instrument provides high sensitivity for the detection of interband and defect luminescence in a variety of infrared detector materials. The spectrometer utilizes a solid state photomultiplier detector and a circular variable filter, which serves as the resolving element. The entire spectrometer is cooled to 5K in order to decrease thermal radiation emission. Band-edge luminescence at 10.1 microns from HgCdTe samples has been readily detected with argon-ion laser excitation powers less than 70 mW/cm2. Representative spectra from HgCdTe and other infrared detector materials are presented.
Photoluminescence and Photomodulation Spectroscopy of CdTe/Cd1−xMnxTe:In Multiple Quantum Wells
Authors: Jiang S. , Zhang L.J. , Zhang J.M. , Shen S.C. 
Published: April 2011

AbstractThe photomodulated reflectivity (PR) spectroscopy of modulation-doped diluted magnetic semiconductor Cd0.72 Mn0.28 Te:In/CdTe multiple quantum wells has been measured at 20 K – 300 K. Several spectral features associated with intersubband transitions have been found. The feature associated with Fermi level is first reported in PR spectra of II–VI heterostructures. In addition, a abnormal transition intensity ratio of 22H to 11H caused by electron filled effect has been reported. The Photoluminescence(PL) spectra of the sample have also been measured at 10 K – 300 K. A strong enhancement of the photoluminescence intensity towards the electron Fermi energy, which is caused by multiple electron-hole scattering processes, is reported. The temperature dependence of the Fermiedge singularity has been measured and discussed. The mechanism of the Fermi-edge singularity can be explained by hole localization.
Toward a Practical Model of a-Si:H Defects in Intensity-Time-Temperature Space
Authors: Caputo D. , Bullock J. , Gleskova H. , Wagner S. 
Published: April 2011

ABSTRACTIn this paper we develop a model of the defect kinetics in hydrogenated Amorphous silicon (a:Si:H) with the goal of predicting the density of defect states g (E) established by any given light intensity I, for arbitrary times t and temperatures T. While we build on widely accepted expressions for the the rates of light-induced and thermal annealing, we examine in more detail the light induced annealing (LIA) term. The model shows that the LIA process can be described with the thermal annealing term if a suitable reduction to the annealing energy is introduced. This reduction depends on the light intensity such as to suggest a relation to the shift of the electron quasi-Fermi level under illumination.
Thermally Stimulated Conductivity in a-Si:H at low Temperatures
Authors: Zhu M. , Von Der Linden M.B. , Van Der Weg W.F. 
Published: April 2011

ABSTRACTThe low temperature thermally stimulated conductivity (TSC) in a-Si:H film has been investigated in the temperature range from 20 to 150 K. Unlike the results of the high temperature TSC, the low temperature peak value and position (Tm) of TSC do not depend on the starting temperature T0 at low temperatures. This new phenomenon can not be explained by TSC theory [1]. Based on the multiple trapping (MT) Model, TSC theory limits its application to the intermediate and high temperature range. In this paper, a model of the hopping conduction with the transport energy Et in the band tail is proposed to understand the behavior of the low temperature TSC in which the thermal emission energy Em does not depend on the starting temperature of TSC.
In-Situ Crystallization and Doping of a-Si film by means of Spin-On-Glass
Authors: Sakoda Tomoyuki , Kim Chang-Dong , Matsumura Masakiyo 
Published: April 2011

ABSTRACTA novel technique has been proposed for selective and in-situ excimer-laser crystallization and doping to thin poly-Si films. Dopant atoms are supplied, during the Si laser crystallization process, to the Si film on glass from the doped SOG (spin-on-glass) film coated on the top. Conductivity of the processed film was increased to more than 10S/cm from about 10−8S/cm of the starting film. This technique has been applied to the bottom gate Amorphous-Si TFTs with self-aligned poly-Si source and drain. The electron field-effect mobility was 1.0cm2/Vs and the on/off current ratio was more than 106. No parasitic effects were observed, and the hole conduction was effectively suppressed. This in-situ crystallization and doping technique can also be applied to the top gate a-Si TFT process.
The Electronic Structure of a-Si,Ge:H Alloys
Authors: Zhong F. , Cohen J.D. , Yang J. , Guha S. 
Published: April 2011

ABSTRACTWe have carried out a detailed study of the energy distribution of deep defects for high quality glow discharge a-Si,Ge:H alloys using both thermal emission and optical Methods: drive-level capacitance profiling, transient photocapacitance and photocurrent plus modulation photocurrent spectroscopy. Four distinct bands of transitions involving defect states have been identified: two associated with thermal transitions, and the other two related to optical transitions. We have, for the first time, observed a negative signal in the photocapacitance spectra at photon energies near 1.2eV. This striking aspect verifies the presence of a distinct defect band above Ep from which electron thermal emission is greatly suppressed. Our Measurements also disclose a fairly narrow defect band below the Fermi level which contrasts with the defect properties observed in a-Si:H. Time resolved photocapacitance spectra indicate that this defect band exhibits configuration relaxation.
The Mechanism of the Plasma Induced Deposition of a-Ge and μc-Ge from Germane: The limits and Possible Alternatives
Authors: Glatz F. , Konwitschny R. , Vepřek-Heijman M.G.J. , Vepřek S. 
Published: April 2011

AbstractTime resolved mass spectrometry and the measurement of appearance potentials of various GeH -cationic fragments combined with selfconsistent theoretical modelling have been used to study the mechanism of plasma induced deposition of germanium. It is shown, that the high rate deposition occurs via germylene, GeH as the direct precursor. Digermane May play some role only at low deposition rates. Although we could reproduce the best values of theμτ product reported so far, no further improvement could be achieved.
Minority Carrier Diffusion Lengths And Photoconductivity In a-Si,N:H Deposited By Remote Pecvd
Authors: Williams M.J. , Cho S.M. , He S.S. , Lucovsky G. 
Published: April 2011

ABSTRACTWe have deposited films of a-Si,N:H by remote PECVD from N2 and SiH4 for N-concentrations, [N], to about 12 atomic percent (at. %). Bonded-H concentrations were ∼7–10 at. %, Mostly in Si-H groups. The films with [N] = 9–12 at. % have εθ4 bandgaps of ∼2.0 to 2.2 eV, which makes them potentially useful as wide bandgap photo-active materials in tandem PV cells. Several properties are of special interest for PV applications. First, like many other a-Si:H-based alloys, the photoconductivity relative to a-Si:H is degraded by alloying, but less than for a-Si,C:H alloys with the same bandgaps. Second, the ambipolar diffusion lengths (Ld) obtained with the Steady State Photocarrier Grating (SSPG) technique for films with [N] = 10 at. % and εθ4 = 2.1eV, are comparable to those of a-Si:H. For lightly-nitrided films to [N] ∼5 at. %, Ld first decreases with respect to a-Si:H and then increases as [N] increases from ∼7 at.% to 10–12 at. %. These trends follow the dark conductivity activation energy, Ea, which initially drops due to doping, and then increases into an alloy regime for [N] > 5 at. %. Films with [N1=10 at. % have dark conductivities and Ea's comparable to those of undoped a-Si:H. Third the magnitude of the Staebler-Wronski effect, as monitored by the photo- to dark conductivity ratio after a 1000 Minute lightsoak, was about the same as in a-Si:H. Finally, we contrast the properties of these films prepared from N2 with a-Si,N:H alloys with the same [N] and E04, but prepared from an ammonia N-atom source gas and attribute differences in their photoelectronic behavior such as a significantly enhanced Staebler-Wronski effect.to the presence of Si-NH bonding arrangements in the films grown from NH3.
Boron and Phosphorus Ion Implantation In a-SixC1−x:H Thin Films
Authors: Rizzoli R. , Galloni R. , Summonte C. , Demichelis F. , Pirrp C.F. , Tresso E. , Crovini G. , Rava P. , Zignani F. 
Published: April 2011

ABSTRACTIn this paper we report results on the optoelectronic and structural properties of device-quality a-SixC1−x:H intrinsic films with energy gap of 1.94 eV and Urbach energy of 70 MeV, grown by PECVD of SiH4+CH4 Mixture, which have been doped by means of boron or phosphorus ion implantation. Doping levels varied in the range 1018 to 5×1020 atoms/cm3. The behaviour of electrical characteristics, as well as energy gap and defect density, Measured on samples annealed in the range 150–400°C, showed that the optimum annealing temperature for the recovery of radiation damage is in the range 250–270°C independent of the implanted dose. Our results also show that after ion implantation and annealing, an increase of the SiH bonds concentration is detected, which is associated to a decrease of the contribution of SiH2, SiCH3, and SiCH vibrations in IR spectra.
Excitation Frequency-Dependent Raman Scattering in a-Sic:H Alloys
Authors: Morel G. , Katiyar R.S. , Weisz S.Z. , Balberg I. 
Published: April 2011

ABSTRACTWe have carried out a comprehensive Raman scattering study of a-S1-xCx:H alloys using three laser excitations: 458, 514, and 581 nm. The alloys studied were prepared with and without H2 dilution, had carbon concentrations, x, between 7 and 20 at %, and Taue optical gaps in the range of 1.8 ≤ Eg ≤ 2.2 eV. The results obtained explain the previous conflicting reports in the literature regarding the Si network disorder and indicate that in the Si-rich compositions, chemical clustering takes place with increasing carbon content.
Nitrogen: Not a Dopant in Crystalline Si (C-Si), But an N-Type Dopant in A-Si:H, Why?
Authors: Lucovsky G. , Williams M.J. , He S.S. , Cho S.M. , Jing Z. , Whitten J.L. 
Published: April 2011

ABSTRACTWe have incorporated N-atoms into hydrogenated amorphous silicon in the Si-rich alloy regime to ∼12 at.% N, and have observed a transition from n-type doping to alloying as the concentration of N-atoms is increased above about 5 at.%. By analogy with the local bonding arrangements of P-donors in n-doped a-Si:H, we attribute the doping to four-fold coordinated N-atoms with second neighbor H-atoms as in N+-Si-H linkages. The occurrence of these arrangements is supported by (i) IR studies which indicate a non-statistical association of N and H-atoms bonded to the same Si-atom, and (ii) a chemical bonding model in which the large effective electronegativies of four-fold coordinated N+ atoms and neutral O-atoms promote similar bonding properties with respect to their nearest-neighbor arrangements with Si and H atoms such as N+ (O) -Si-H linkages
Identification and Reduction of P-I Interface Instability and Establishment of 8.5% Stabilized Efficiency for Single Junction a-Si Solar Cells
Authors: Xi Jianping , Liu Tongyu , Iafelice Vincent , Si Kevin , Rampas Frank 
Published: April 2011

ABSTRACTOur previously reported 7.5% stabilized efficiency single junction a-Si devices had relatively low Voc, around 0.80 volts. Devices with higher Voc tended to exhibit a decrease in Voc upon light soaking. This effect was found to be independent of the properties of the i-layer. Further optimizing the p layer and p-i interface has enabled us to produce single junction devices with a stable Voc of up to 0.86 volts and a 8.5% stabilized device efficiency has been established.
Adjusting the Defect Profile in a-Si:H Solar Cells with Energy Resolved Electron or Laser Beams: Experiment and Modeling
Authors: Vasanth K. , Caputo D. , Wagner S. , Bennett M. , Bae S. , Fonash S. 
Published: April 2011

ABSTRACTWe light-soaked a-Si:H pin solar cells with blue laser light through the front glass substrate or electron irradiated them through the back Al layer. By using short wavelength light and energy resolved electron beams we localize the damage preferentially near the p/i or n/i interface and thus study their effect on cell performance. I-V characteristics and quantum efficiency spectra were measured before and after the damage was introduced. We Modeled the changes in the quantum efficiency using the numerical device Model AMPS. Comparing changes in the measured and modeled quantum efficiencies (QE) we find that cells light-soaked with the blue laser have damage localized near the front of the device, and localized near the back for cells irradiated with electrons. This indicates that quantum efficiency measurements are sensitive to the location Of defects in the i-layer of the solar cell. However after long light-soaking and electron irradiation times the difference between the two types of damage becomes less visible in the QE Measurements.
In Situ Ellipsometric Monitoring of Low Temperature Growth of Poly-Si Films By RF Plasma CVD
Authors: Shirafuji T. , Hayashi Y. , Tachibana K. 
Published: April 2011

ABSTRACTIn situ ellipsometry has been applied for monitoring silicon-thin-film growth on a glass substrate in RF-discharge plasma of SiF4+SiH4 diluted with H2 (80%). Polycrystalline silicon films were obtained at substrate temperature of 300°C and RF power density of 500MW/cm2. Volumetric fraction of c-Si increased from 50 to 80% by increasing the SiF4/ (SiF4+SiH4) flow ratio from 0 to 0.5. The fraction of c-Si also increased to 63% by sequential repetition of deposition with SiH4/H2 and etching with SiF4. The etching rate of a-Si was less than that of c-Si. These results suggest that semi-preferential etching of a-Si enhances the increase of c-Si fraction. A gas-phase reaction simulation has suggested that the dominant deposition precursor is SiH3, and the etchant is F in the present condition.
Silicon Nitride Optimisation for A-Si:H Tfts Used in Projection LC-TVS
Authors: French I. D. , Curling C. J. , Goodyear A.L. 
Published: April 2011

ABSTRACTMulti-layer devices based on thin films in Large Area Electronics have different intrinsic and extrinsic properties that must be optimised to produce the correct physical shape of the device, in addition to having acceptable electrical characteristics. For instance it is quite easy to produce individual layers optimised for electrical performance that will physically “pull off’ underlying films, or result in poor step coverage. The factors that must be considered include mechanical stress, etching rates and profiles, thickness and stoichiometry uniformity, and thermal budgets, as well as electrical characteristics. This paper gives an example of silicon nitride optimisation for use in a-Si:H TFT projection displays. Three different silicon nitride layers were included to give a storage capacitor, together with controlled etch profiles for step coverage. The layers were optimised with respect to several different parameters in the minimum number of depositions by the use of experimental design techniques.
Effects of N2 Plasma Treatment on SiO2 Gate Insulator in a-Si:H Thin Film Transistor
Authors: Kim Sung Chul , Bae Sung Sig , Oh Eui Yeol , Kim Jeong Hyun , Lee Jong Wan , Kim Cha Yeon , Kim Donggil 
Published: April 2011

ABSTRACTWe fabricated the high performance a-Si:H TFT using the N2 plasma treated APCVD SiO2 as a gate insulator. The effects of N2 plasma treatment on the APCVD SiO2 were investigated by XPS and SIMS Measurements. And the formation of the oxynitride interface layer between a-Si:H and APCVD SiO2 was found in the a-Si:H TFT. From our experimental results, It May be concluded that most nitrogen atoms, which were incorporated by the exposure of SiO2 layer to N2 plasma, exist, not bonded to other atoms, near the surface of the SiO2 layer and during the sequential deposition of a-Si:H on the N2 plasma treated APCVD SiO2 layer Si-N bonds are formed, resulting in the oxynitride layer in the interface region. This explains the high performance a-Si:H TFT with the N2 plasma treated APCVD SiO2 gate insulator.
Stability of a-Si:H TFTs Employing APCVD SiO2 with N2 Plasma Treatment as a Gate Dielectric
Authors: Jun M.C. , Kim Y.S. , Oh E.Y. , Kim D.G. , Han M.K. 
Published: April 2011

ABSTRACTWe have investigated the stability of the hydogenated amorphous silicon thin film transistors (a-Si:H TFTs) employing silicon dioxide (SiO2) with N2 plasma treatment as a gate dielectric, where SiO2 was deposited by atmospheric pressure chemical vapor deposition (APCVD). Their stability was compared with those of a-Si:H TFTs whose gate dielectric was silicon nitride (SiNx) deposited by plasma enhanced chemical vapor deposition (PECVD). Two kinds of stresses, gate bias and light illumination, were applied. The threshold voltage shin (AVu,) and the inverse subthreshold slope shift (ΔVth) were measured as a function of the bias voltage and the light stress time. For the positive bias stress, the ΔVth, of the a-Si:H TFTs with the N2 plasma treated SiO2 dielectric is smaller than that with the PECVD SiNx gate dielectric. For the negative bias stress and light stress, however, the ΔVth of TFT with N2 plasma treated SiO2 dielectric is larger than that with the SiNx dielectric
Density of Deep Bandgap States in Amorphous Silicon From the Temperature Dependence of Thin Film Transistor Current
Authors: Globus T. , Slade H. C. , Shur M. , Hack M. 
Published: April 2011

ABSTRACTWe have measured the current-voltage characteristics of amorphous silicon thin film transistors (a-Si TFTs) over a wide range of temperatures (20 to 160°C) and determined the activation energy of the channel current as a function of gate bias with emphasis on the leakage current and subthreshold regimes. We propose a new method for estimating the density of localized states (DOS) from the dependence of the derivative of activation energy with respect to gate bias. This differential technique does not require knowledge of the flat-band voltage (VFB) and does not incorporate integration over gate bias. Using this Method, we have characterized the density of localized states with energies in the range 0.15–1.2 eV from the bottom of the conduction band and have found a wide peak in the DOS in the range of 0.8–0.95 eV below the conduction band. We have also observed that the DOS peak in the lower half of the bandgap increases in magnitude and shifts towards the conduction band as a result of thermal and bias stress. We also measured an overall increase in the DOS in the upper half of the energy gap and an additional peak, centered at 0.2 eV below the conduction band, which appear due to the applied stress. These results are in qualitative agreement with the defect pool Model [1,2].