bluuebunny/crossref_metadata_2025_split huggingface dataset:
Al/ZnO/a-SiGe:H: A System Protected by the ZnO Buffer from Metal-Induced Crystallization
Authors: Edelman F. , Brener R. , Cytermann C. , Weil R. , Beneking C. , Beyer W. , Skorupa W. , Yankov R. , Werner P. 
Published: April 2011

ABSTRACTMetal-Induced-Crystallization (MIC) by the contact of amorphous semiconductors with metals is one of the degradation factors in solar cells. This study has been made on the barrier properties of a ZnO layer between undoped a-SiGe:H and Al metallization films in the structure (001)Si/SiO2/a-SiGe:H/ZnO/Al. Plasma assisted CVD deposition was used to produce a-Si1.xGex:H (x=0 to 1) undoped films over thermally oxidized Si-wafers. There were covered with 500Å and 1000Å thick transparent conductive layers of ZnO. Al and then 1000Å thick films of Al. A set of Al-implanted a-Si, a-Ge, and a-Sio.5Geo.5 films on Si/SiO2 substrates was also prepared to study MIC in an amorphous system with dispersed Al. The structures were annealed in vacuum in the temperature range of 200°C to 400°C for lh. X-ray diffraction studies demonstrated the a-SiGe:H stability against crystallization under ZnO protection up to 400°C. Secondary Ion Mass Spectroscopy didn't reveal any noticeable redistribution of Al inside Al-implanted a-Si:H and a-Si0.5Ge0.5:H samples after annealing at 400°C for lh, but strong Al diffusion was seen in the a-Ge:H layer. Nevertheless, no MIC was observed in any of the Al-implanted a-materials.
Impact of Hydrogen Dilution on the Properties and Light Induced Changes of A-SI:H Based Materials and Solar Cells
Authors: Lee Yeeheng , Jiao Lihong , Koh Joohyun , Fujiwara Hiroyuki , Lu Zhou , Collins R. W. , Wronski C. R. 
Published: April 2011

ABSTRACTStudies have been carried out on a-Si:H materials and corresponding solar cells fabricated with and without hydrogen dilution of silane by rf PECVD. The effect of hydrogen dilution on the growth kinetics and microstructures and their dependence on the substrate temperature have been studied. Hydrogen diluted a-Si:H materials and solar cells exhibit improved properties and higher stability to light induced changes. Distinct differences are found in the electron mobility lifetime (μτ) products and subgap absorption over a wide range of generation rates. Striking differences are also found in the kinetics of light induced degradation in both the materials and their corresponding solar cells. Direct correlations are presented between the degradation kinetics of p(a-SiC:H)/i(a-Si:H)/n(μc-Si) solar cells and those of thin film materials constituting the i-layers.
Energy Dependence of Defects in a-Si:H Solar Cells During Degradation and Annealing Processes
Authors: Caputo Domenico , Lemmi Francesco , Palma Fabrizio 
Published: April 2011

ABSTRACTIn this work we report on the effect of current-induced degradation and annealing on p-i-n amorphous silicon solar cells. Current-voltage curves and capacitance measurements under forward bias have been used to monitor the current-induced changes as a function of time. We found that the recovery rate increases with the annealing current, while the stabilized value of efficiency decreases. Comparison of short circuit current and capacitance evolution suggests that defect kinetics in the electronic gap occurs in a different way during degradation and annealing. This behavior can be modeled assuming a faster annealing of defects closest to the extended band and a slower annealing of mid-gap defects.
The Effect of the Amorphous Silicon Alpha-Gamma Transition on Thin Film Transistor Performance
Authors: French I D , Deane S C , Murley D T , Hewett J , Gale I G , Powell M J 
Published: April 2011

ABSTRACTWe have investigated the effect of depositing amorphous silicon (a-Si:H) under α and γ (or dusty) plasma conditions on hydrogen bonding and TFT performance. By infrared measurements three deposition regimes could be identified due to their distinctive absorption curves in the bending mode range of 800 to 900 cm'1. These corresponded to a films deposited below 300°C, γ films deposited below 300°C, and films deposited in either plasma condition at temperatures of 300°C and above. There was a correlation between the a-Si:H material regimes and TFT performance. When the deposition temperature was below 300°C the a-TFTs had a higher field effect mobility than γ-TFTs, but lower stability. For deposition temperatures of 300°C and above the films had more similar properties regardless of whether they were deposited under a or γ conditions. TFT mobilities were the same, but TFTs containing a-Si:H deposited under γ conditions were still more stable. These results show that the mobility and stability of TFTs are optimised for different growth conditions, and that the overall best conditions for TFT manufacture depends upon the specific application.
The Impact of Field Plate Resistivity on the Performance of a Novel High Voltage Thin Film Transistor Incorporating a Semi-Insulating Layer
Authors: Chen Y. , Clough F. J. , Sankara Narayanan E. M. , Xu Y. Z. , Eccleston W. , Milne W. I. 
Published: April 2011

ABSTRACTThe Semi-Insulating field plated High Voltage TFT (SI HVTFT) is a new poly-Si HVTFT structure with a much improved blocking capability and enhanced on-state performance [1][2]. The unique feature of the SI HVTFT is the semi-insulating amorphous oxygen-doped Si (SIAOS) field plate which connects the gate to the drain and reshapes the potential distribution in the offset region. The leakage current, flowing through the SIAOS field plate during device operation, determines device performance. In this paper, both experimental and 2-D simulation results for devices with different field plate conductivities are used to investigate the impact of the field plate properties on the performance of the SI HVTFT structure.
Microstructures of GaN Films Grown on a LiGaO2 New Substrate by Metalorganic Chemical Vapor Deposition
Authors: Li Jing-Hong , Kryliouk Olga M. , Holloway Paul H. , Anderson Timothy J. , Jones Kevin S. 
Published: April 2011

ABSTRACTMicrostructures of GaN films grown on the LiGaO2 by metalorganic chemical vapor deposition (MOCVD) have been characterized by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). TEM and HRTEM results show that high quality single-crystal wurtzite GaN films have been deposited on the LiGaO2 and that the GaN film and the LiGaO2 have the following orientation relationship: (2110)(0002)GaN ̂ (002)LiGaO2 ^ 5–8°. A higher density of threading dislocations and stacking faults have been observed near the GáN/LiGaO2 interface, even though the lattice mismatch of GaN to LiGaO2 is only ∼1%. Threading dislocations with burgers vector b=<0001> and b=a/3<1120> are predominant in the GaN films. Also the GaN films contain some columnar inversion domain boundaries (IDBs). Both TEM and HRTEM results reveal that there is an unexpected amorphous or nano-crystalline inter-layer between the GaN and the LiGaO2 with a thickness of 50–100 nm.
Tem/Hrem Analysis of Defects in GaN Epitaxial Layers Grown by MOVPE on SiC and Sapphire
Authors: Ruvimov S. , Liliental-Weber Z. , Dieker C. , Washburn J. , Koike M. , Amano H. , Akasaki I. 
Published: April 2011

ABSTRACTHigh resolution electron microscopy has been applied to study the structure of epitaxial GaN layers grown by MOVPE on SiC and sapphire substrates. Defects in GaN were systematically studied for undoped, and Si- and Mg-doped samples. For both substrates, the Si-doping was found to decrease the dislocation density at the layer surface, while Mg-doping increased it. The density of nanopipes increased with both types of doping. Cracking of GaN layers was observed for SiC substrates. Crack formation was not detected in layers grown on sapphire. Mechanisms of defect generation are discussed in relation to the initial growth stages, the effect of doping, and the type of substrate.
Characterisation of AlxGa1-xN Films Prepared by Plasma Induced Molecular Beam Epitaxy on C-Plane Sapphire
Authors: Angerer H. , Ambacher O. , Stutzmann M. , Metzger T. , Höpler R. , Born E. , Bergmaier A. , Dollinger G. 
Published: April 2011

ABSTRACTAlxGa1-xN films were grown on c-plane sapphire by plasma induced molecular beam epitaxy with 0 ≤ x ≤ 1. The composition and purity of the AlxGa1-xN layers was determined by elastic recoil detection analysis with a relative error of 5% for the Al content. Both X-ray diffraction and atomic force microscopy indicate only a slight decrease in epitaxial quality of the AlxGa1-xN films with increasing Al content up to x = 0.65. X-ray diffraction is used to separate the effects of thermally induced biaxial compressive stress and the alloy composition on the shift of interplanar spacings by measuring both lattice constants. The deviation of the c/a ratio from that of fully relaxed films is a quantitative measure of the biaxial compressive stress leading to a distortion of the unit cell. Values up to 0.5 GPa were observed. By the method proposed, the determination of alloy composition can be corrected for this effect. The results obtained by this method are in very good agreement with the elastic recoil detection measurements substantiating the validity of Vegard's law. These results, compared with optical measurements, indicate that the bowing parameter of the optical bandgap is 1.3 eV within the experimental error.
The Atomic Structure of the {1010} Inversion Domains in GaN/Sapphire Layers
Authors: Potin V. , Ruterana P. , Nouet G. , Salvador A. , Morkoç H. 
Published: April 2011

ABSTRACTNanometric inversion domains in GaN/Al2O3 layers have been investigated using HREM. They were found to be limited by {1010} planes and to cross the entire epitaxial layer. It has been possible, using extensive image simulation and matching to discriminate between possible atomic models for the boundary plane. It is shown that the inversion domain boundaries correspond to a Holt type model containing wrong bonds (Ga-Ga, N-N), and in that plane, each atom exhibits two such bonds. This probably can explain the small size of the domains (5–20 nm).
Etch Characteristics of GaN Using Inductively Coupled Cl2/HBr and Cl2/Ar Plasmas
Authors: Kim H. S. , Lee Y. J. , Lee Y. H. , Lee J. W. , Yoo M. C. , Kim T. I. , Yeom G. Y. 
Published: April 2011

ABSTRACTTo fabricate GaN-based optoelectronic devices successfully, a reproducible etch process with high etch rates, vertical etch profile, and damage-free surface is required. In this study, GaN etching was performed using planar inductively coupled plasmas and the effects of process parameters such as inductive power, bias voltage, pressures and, gas combination on the characteristics of the plasmas were studied using Langmuir probe, optical emission spectroscope (OES), and quadrupole mass spectrometer (QMS). Gas combinations of Cl2/Ar and Cl2/HBr were used to etch GaN. GaN etch rates increased with the increase of chlorine radical and ion energy (bias voltage), and the etch rates close to 4000 Å/min could be obtained without substrate heating over 100 °C. The addition of HBr and Ar (more than 20%) generally reduced GaN etch rates. In our experimental condition, it appears that the chemical reaction between Cl and Ga in GaN affects more significantly to GaN etching compared to physical sputtering, and it was partially confirmed by the data measured by Langmuir probe and OES. Angle resolved XP S data showed the variation of surface Ga/N ratio depending on the process parameters, which influence the formation of low resistance ohmic contact.
Electron Field Emission from Aluminum Nitride
Authors: Malta D. P. , Fountain G. G. , Posthill J. B. , Humphreys T. P. , Pettenkofer C. , Markunas R. J. 
Published: April 2011

ABSTRACTAlN has been identified as a candidate material for cold cathode field emitters due to its purported negative electron affinity (NEA) surface. Recent studies by our group on AlN(0001) using angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and scanning electron microscopy (SEM) have indicated that AlN(0001) is a positive electron affinity surface. We have also investigated electron field emission behavior of AlN and pure Al films grown on Si. AlN and Al films were grown by molecular beam epitaxy (MBE) and transported via an ultra-high vacuum (UHV) integrated processing system (IPS) to an electron emission measurement system (EEMS). The reference Al film on Si showed characteristic Fowler-Nordheim behavior with a turn-on field of 120V/μm (defined at 10μA-cm-2) and ∼100μA-cm-2 emission at 140V/μm. The AlN film also showed Fowler-Nordheim behavior with a turn-on field of 60V/μm and ∼10mA-cm-2 at 100V/μm. Air exposure of the AlN film caused a shift in turn-on to 90V/μm and ∼0.1mA-cm-2 at 100V/μm. The I-V behavior of the AlN film is consistent with the ARUPS results on a different AlN sample - both indicating a positive electron affinity AlN surface.
MOCVD Growth of High Output Power Ingan Multiple Quantum Well Light Emitting Diode
Authors: Kozodoy P. , Abare A. , Sink R. K. , Mack M. , Keller S. , DenBaars S. P. , Mishra U. K. , Steigerwald D. 
Published: April 2011

ABSTRACTThe MOCVD growth of InGaN / GaN multiple quantum well (MQW) structures for optoelectronic applications has been investigated. The structural and optical properties of the layers have been characterized by x-ray diffraction and photoluminescence. The effect of barrier and well dimensions on the optical properties have been examined; highest emission intensity and narrowest linewidth were obtained with thin wells (20–30 Å) and thick barriers (greater than 50 Å). By incorporating an MQW structure as the active region in a GaN p-n diode, high-brightness light emitting diodes (LEDs) have been produced. Under a forward current of 20 raA, these devices emit 2.2 mW of power corresponding to an external quantum efficiency of 4.5%. The emission spectrum peaks at 445 nm and exhibits a narrow linewidth of 28 nm. Under pulsed high current conditions, output power as high as 53 mW was realized and the peak emission wavelength shifted to 430 nm.
Growth of GaN Thin Films on Sapphire Substrate by Low Pressure MOCVD
Authors: Ishida M. , Hashimoto T. , Takayama T. , Imafuji O. , Yuri M. , Yoshikawa A. , Itoh K. , Terakoshi Y. , Sugino T. , Shirafuji J. 
Published: April 2011

ABSTRACTHigh quality GaN films are grown on sapphire(0001) substrates by low pressure MOCVD using TMG and NH3 as source materials. Effects of surface nitridation and buffer layer thickness on the quality of over-grown GaN films are investigated. It is revealed by atomic force microscope (AFM) observations that surface roughness of the annealed buffer layers strongly depends on the nitridation time. Dislocation density and surface morphology of the high temperature GaN layer depend on the buffer layer thickness. It is found that sufficient surface nitridation of sapphire makes the buffer layer just prior to the high temperature growth very smooth, which is essential to obtain flat thick-GaN on it. It is also found that thickness of the buffer layer largely influences the dislocation density in the over-grown thick GaN. In order to obtain good surface morphology and low dislocation density at the same time, both nitridation time and buffer layer thickness must be optimized.
Comparison of SiH4 and Si2H6 RTCVD Kinetics using in-situ Spectroscopic Ellipsometry
Authors: Hu Y. Z. , Tay S. P. , Wasserman Y. , Zhao C. Y. , Irene E. A. 
Published: April 2011

ABSTRACTA comparison of SiH4 and Si2H6 chemical vapor deposition kinetics was performed in a rapid thermal processing (RTP) system at temperatures between 600 and 800 °C and reactant gas pressures between 1 and 25 mTorr. Quantitative assessment of the nucleation parameters and the microstructures of the deposited polycrystalline Si (poly-Si) films on SiO2 have been determined using in situ real time single wavelength and spectroscopie ellipsometry. In addition to ellipsometry, atomic force microscopy and cross-sectional transmission electron microscopy were used ex situ to observe the nucleation stage and the microstructures of the poly-Si films. In the present study we compare the nucleation, poly-Si film microstructure and surface roughness using SiH4 and Si2H6 in the RTP system and show that under the same processing conditions the saturation nuclei density (1010 cm−2) for Si2H6 is about 6 times higher than that for SiH4 and the poly-Si films from Si2H6 are smoother and have better columnar structure than those from SiH4.A particularly important parameter for selective epitaxial depositions is the time for nuclei to form, i.e. the incubation time. An operational incubation time were determined from the real time ellipsometric measurements and confirmed by AFM. The incubation times for using SiH4 and Si2H6 are different, but they show similar activation energies of about Einc = 1 eV in the 600–800 °C range. A formula of incubation time tinc was obtained and expressed.
Study of Repeatability, Relative Accuracy and Lifetime of Thermocouple Instrumented Calibration Wafers for RTP
Authors: Vandenabeele Peter , Renken Wayne 
Published: April 2011

ABSTRACTAn RTP system with accurate lamp power control was used to study the repeatability of Sens Array type “1530” and “1501” thermocouple (TC) wafers. The drift of the “1530” wafers was measured over 200 heating cycles of 20 seconds at 1050 °C and 1150 °C. Over the 200 cycles at 1150 °C, a drift between -0.5 and +1.0 °C was found. Over the 1050 °C cycles a larger drift between +1.0 °C and +2.0 °C was found, possibly caused by the formation of “haze” over the wafer that changed the optical properties of the wafer. Experiments were conducted for the effect of unloading/loading of the wafer in the oven. An instability of maximum ±0.4 °C was found for “1530”, caused by the unloading/loading. The relative accuracy of “1530” from one thermocouple to another shows a typical variation of ±1.0 °C or smaller. The older technology TC wafers (1501), showed considerably higher instability upon wafer unloading/loading and higher TC to TC variations (± 5 °C). The useful lifetime of a TC wafer is at least 50 to 200 heating cycles.
The Influence of Facility Conditions on A ±0.25 °C Repeatability Lamp Voltage Controlled RTP System
Authors: Vandenabeele Peter , Renken Wayne 
Published: April 2011

ABSTRACTThe influence of cooling air and cooling water parameters on the wafer temperature was studied in an RTP system with lamp power control. With a cool down time of 150 seconds between consecutive heating cycles, the wafer temperature in a 1050 °C process was highly sensitive to cooling air flow. With a cool down time of 330 seconds the sensitivity dropped a factor of 5. This was explained through the effect of radiative heat transfer from the quartz to the wafer at higher quartz temperatures (>200 °C). Other factors are variations in the water flow through the oven walls and the repeatability of wafer positioning.
Characterization of Oxide Etching and Wafer Cleaning using Vapor-Phase Anhydrous HF and Ozone
Authors: Froeschle Barbara , Deutschmann Lutz , Bauer Anton J. , Burte Edmund P. 
Published: April 2011

ABSTRACTA cleaning process using anhydrous HF (AHF)/methanol and ozone is carried out in a STEAG-AST Vapor Phase Cleaning module (VPC). This module is integrated in a state-of-the-art cluster tool also consisting of a STEAG-AST Rapid Thermal Oxidation module (RTO). The dependence of AHF vapor phase etch rate of thermally grown silicon dioxide on different process parameters, such as etch time, AHF-flow, and temperature is evaluated. The optimized etch process is found to be at a temperature of 40°C and at a pressure of 50 mbar for this VPC module. Using the above etch parameters various combinations of vapor phase surface preparation chemistries combining AHF etching and ozone/UV cleaning are evaluated.To demonstrate the feasibility of this cluster tool for advanced gate dielectric formation, 4.0 nm thin oxide is grown directly after the cleaning in the RTO module without breaking the vacuum. Time dependent dielectric breakdown results for oxides pre-oxidation-cleaned in AHF, and in AHF followed by ozone are compared to a reference sample without any dry pre-oxidation cleaning. It can be shown, that the cleaning in AHF with a subsequent ozone step at 200°C under UV light leads to improved breakdown characteristics compared to AHF/methanol cleanings without such subsequent ozone/UV step or conventional wet cleaning using HF-Dip.
An Interactive System for Wafer Emissivity Estimation as Determined in an RTP Chamber
Authors: Fulco Maurizio , Russo Onofrio L. , Belikov Sergey , Kosonocky Walter 
Published: April 2011

ABSTRACTWe demonstrate an interactive software system in which the emissivity of wafers can be estimated in situ using different models. The system allows the data taker to introduce a choice of design parameters necessary for the control of temperature uniformity. The objective of the interactive system is to obtain a better estimation of the wavelength dependent emissivity by using existing data such as integrated emissivity, for example, as input information. Results for some of the models are presented and compared to show differences in the models chosen. The principle advantage offered by the system are the likely prospects of a realistic improvement and confident assessment for real time temperature measurement and control in an RTP environment.
Deep Level Investigation in Si-GaAs by Rapid Thermal Annealing
Authors: Zhouying Zhao , Fengmai Wu , Ningsheng Li 
Published: April 2011

ABSTRACTDeep levels in undoped LEC semi-insulating (SI) GaAs have been investigated by rapid thermal annealing (RTA). The GaAs wafers were annealed for 10 sec in N2 atmosphere at temperatures ranging from 500 to 800 °C. Using photo-induced current transient spectroscopy (PITS) and Hall measurement, we have investigated the behavior of various deep levels as a function of RTA temperature and the phenomenon of thermal conversion. The change and even conversion in resistivity is related not only to decrease of the EL2 and EL6 defects, but also to shallow acceptor caused by arsenic-escaping in the surface of the wafer. Choosing proper RTA temperaturte will improve the electrical properties of SI-GaAs after RTA.
Growth and Nitridation of Silicon-Dioxide Films on Silicon-Carbide
Authors: Sweatman Denis , Dimitrijev Sima , Li Hui-Feng , Tanner Philip , Barry Harrison H. 
Published: April 2011

ABSTRACTSilicon-carbide offers great potential as a wide bandgap semiconductor for electronic applications. A good quality oxide dielectric will allow MOS device fabrication and in particular N-channel mosfets for their higher electron mobility. To date oxides on N-type silicon-carbide (nitrogen doped) have exhibited excellent characteristics while on P-type (aluminium or boron doped) the characteristics are poor. This paper presents results for the oxidation and subsequent nitridation of N and P-type silicon-carbide. It illustrates the role that nitrogen at the interface has in improving the trap densities and that nitric oxide provides the nitrogen well. Nitrous oxide, previously used to nitride silicon dioxide on silicon, is shown to substantially deteriorate the interface density of states for both N and P-type substrates.