A study of the process of decomposition of supersaturated GaAs:Fe solid solution by scanning probe microscopy

Using an atomic-force microscope, the decomposition of the supersaturated solid solution of iron-doped GaAs (GaAs:Fe) is studied. GaAs:Fe samples were obtained in the course of high-temperature diffusion of Fe into GaAs and subsequent annealing at a temperature by 200°C below the doping temperature. The measurements are performed for transverse cleavages along the cleavage planes of the GaAs:Fe wafers. It is shown that, during annealing of the GaAs:Fe samples, the supersaturated alloy decomposes with the formation of particles of the second phase from ∼50 nm to ∼1 μm in size. The particles of the second phase possess ferromagnetic properties at room temperature.     

退火损伤对Er注入GaAs和Yb注入InP发光的影响

本文报道了CaAs∶Er、InP∶Yb发光样品的二次离子质谱、X-射线双晶衍射测量结果及其与Er离子的表面成份的关系.分析讨论了退火损伤对GaAs∶Er和InP∶Yb发光的影响以及Er~(3+)复合体发光中心模型.     

GaAs surface wet cleaning by a novel treatment in revolving ultrasonic atomization solution

A novel process for the wet cleaning of GaAs surface is presented. It is designed for technological simplicity and minimum damage generated within the GaAs surface. It combines GaAs cleaning with three conditions consisting of (1) removal of thermodynamically unstable species and (2) surface oxide layers must be completely removed after thermal cleaning, and (3) a smooth surface must be provided. Revolving ultrasonic atomization technology is adopted in the cleaning process. At first impurity removal is achieved by organic solvents; second NH_4OH : H_2O_2 : H_2O =1:1:10 solution and HCl : H_2O_2 : H_2O = 1:1:20 solution in succession to etch a very thin GaAs layer, the goal of the step is removing metallic contaminants and forming a very thin oxidation layer on the GaAs wafer surface;NH_4OH : H_2O =1:5 solution is used as the removed oxide layers in the end. The effectiveness of the process is demonstrated by the operation of the GaAs wafer. Characterization of the oxide composition was carried out by X-ray photoelectron spectroscopy. Metal-contamination and surface morphology was observed by a total reflection X-ray fluorescence spectroscopy and atomic force microscope. The research results show that the cleaned surface is without contamination or metal contamination. Also, the GaAs substrates surface is very smooth for epitaxial growth using the rotary ultrasonic atomization technology.     

GaAs表面旋转超声雾化清洗新技术

研究了一种新型湿法化学清洗半导体GaAs表面的方法。通过简单设计清洗工艺能使GaAs表面产生最低的损伤。GaAs表面清洗必须满足三个条件：(1)清除热力学不稳定因素和表面粘附的杂质,(2) 除去GaAs表面氧化层,(3)提供一个光滑平整的GaAs表面。本文采用旋转超声雾化方式用有机溶剂除去GaAs表面的杂质,再用NH4OH:H2O2:H2O= 1:1:10和HCl:H2O2:H2O=1:1:20顺次腐蚀非常薄的GaAs层,去除表面的金属污染,并在GaAs表面形成一个非常薄的氧化层表面,最后用NH4OH:H2O= 1:5溶液来清除GaAs表面氧化层。测试GaAs表面的特性,分别用X射线光电光谱仪、X射线全反射荧光光谱仪和原子力显微镜测试了GaAs表面氧化的组分、GaAs表面金属污染和GaAs表面形貌,测试结果表明通过旋转超声雾化技术清洗可提供表面无杂质污染、金属污染和表面非常光滑的GaAs衬底,以供外延生长。     

Lateral and vertical isolation by arsenic implantation into MOCVD-grown GaAs layers

We have demonstrated the formation of arsenic precipitates in GaAs using arsenic implantation and annealing. Electrical measurements show that very high resistivity (surface or buried) GaAs layers can be produced by this method. The arsenic-implanted materials are similar to GaAs:As buffer layers grown by low-temperature molecular beam epitaxy, which are used for eliminating backgating problems in GaAs circuits. Arsenic implantation is a nonepitaxial process which is compatible with current GaAs technology. Formation of insulating GaAs layers by this technique may improve the performance and packing density of GaAs integrated circuits, leading to advanced novel III–V compound-based technologies for high-speed and radiation-hard circuits.     

Characterization of interface stress at InGaPAs/GaAs by cr-related luminescence line in GaAs

The interface stress at InGaPAs/GaAs heterostructure has been investigated using the energy shift and splitting of the Cr-related zero-phonon photoluminescence line at 0.839 eV observed in GaAs. It has been found that the GaAs substrate suffers both compressive uniaxial stress and tensile hydrostatic pressure at the InGaPAs/GaAs heterointerface. These shifts and splittings of the 0.839 eV line have been systematically examined as a function of the lattice mismatch between InGaPAs and GaAs, and the thicknesses of the epitaxial-layer and substrate. The amount of the interface stress existing at InGaPAs/GaAs heterostructure has been estimated, based on uniaxial stress data for GaAs: Cr wafers.     

抑制高峰值功率皮秒激光放大系统Nd:YAG中的自聚焦效应

全固态皮秒放大器的平均输出功率易受到增益晶体中自聚焦效应的影响。通过引入补偿元件砷化镓（GaAs）片可以避免自聚焦效应造成的损伤，关于砷化镓的抑制机理对高峰值功率Nd:YAG晶体皮秒放大器系统的进行理论分析和实验研究。以公式计算得到了GaAs材料的非线性折射率系数，并由数值模拟给出了在抑制自聚焦的最佳效果下GaAs片厚度与Nd:YAG棒长度的关系。在入射皮秒激光束中心波长为1 064 nm、重复频率为1 kHz、峰值功率密度为12 GW/cm2的条件下，进行了不同厚度（200 m和550 m） GaAs片对抑制Nd:YAG棒自聚焦损伤的实验研究。通过优化GaAs片的厚度，该补偿方法在高峰值功率皮秒脉冲条件下，特别是对于Nd:YAG放大器显示出较高的效率。关键词:自聚焦效应；非线性折射率系数；光学损伤； B积分     

GaAs-GaAlAs anti-Stokes light convertor

A multilayer heterojunction device has been manufactured and used for efficient anti-Stokes light conversion. The device consists of six layers: p GaAs, n GaAs, n GaxAl1?xAs, p GayAl1?yAs, p GaxAl1?xAs and p GaAs, essentially forming a GaAs photodiode coupled with a GaAlAs l.e.d. Avalanche multiplication of photoexcited carriers is used to increase the l.e.d. driving current.     

Ku波段GaAs单片功率放大器

基于GaAs PHEMT在微波领域的卓越性能,设计并实现了两款Ku波段GaAs单片功率放大器。简述了GaAs PHEMT器件的工作原理,并抽取了精准的EEHEMT模型,通过独特的设计方法并结合相应的仿真软件设计了两款Ku波段单片功率放大器。经过精准测试,两款电路呈现的性能如下:在13～14GHz频带内,其中第一款电路的饱和输出功率Po>38dBm(脉宽100μs,占空比10%),功率增益GP>20dB,典型功率附加效率PAE>28%;第二款电路的饱和输出功率Po>40dBm(脉宽100μs,占空比10%),功率增益GP>19dB,典型功率附加效率PAE>28%。结果表明,基于PHEMT的GaAs单片功率放大器在Ku波段可以实现优良的性能。     

Photocapacitance of deep levels in GaAs:Cr and GaAs:O

Photocapacitance measurements have been applied to characterize deep impurities present in bulk-grown single crystals of n-type GaAs:O and GaAs:Cr. Three principal defects in GaAs:O have levels located at (E_c ? 0.79 eV), (E_v + 0.40 eV) and (E_c ? 0.46 eV); the first of these corresponds to the level commonly associa with oxygen and agrees well with the Lucovsky model for photoionization spectrum. The Cr level in GaAs:Cr does not follow the Lucovsky model and appears to undergo “lattice relaxation” during optical transitions.     

Modification of GaAs Schottky barriers using a-Si:H interfaciallayers

The electrical characteristics of metal/a-Si:H/n-GaAs diode structures were studied in order to investigate the role of the a-Si:H and the claim of no barrier at the GaAs/a-Si:H interface. Diodes were fabricated using a-Si:H layers between 30 and 1920 Å thick, with Al and Mg metallization, and the current-voltage and capacitance-voltage characteristics were examined. Rectifying Schottky barriers were formed at Al/a-Si:H junctions, while good ohmic contacts were formed at Mg/a-Si:H junctions, enabling effects due to the metal/a-Si:H and a-Si:H/GaAs interface to be isolated. A dramatic increase in the forward turn-on voltage was observed as the thickness of the a-Si:H layer increased. The diode behavior can be explained by considering three effects in series: (1) an a-Si:H/GaAs barrier of about 0.6 eV, consistent with Fermi-level pinning in GaAs; (2) a metal/a-Si:H barrier, dependent on the metallization; and (3) space-charge-limited current (SCLC) in the bulk a-Si:H. The SCLC effectively gives rise to a voltage-dependent resistance and causes the increased turn-on voltages     

A comparison of gamma-irradiation-induced degradation in amphoterically Si-doped GaAs LED's and Zn-diffused GaAs LED's

A comparison is presented of the effects of gamma irradiation on the properties of amphoterically Si-doped GaAs LED's and Zn-diffused GaAs LED's. It is shown that the light output of GaAs:Si LED's is severely degraded by irradiation, and, in addition, that the light output cannot be recovered through forward-bias-induced annealing. In contrast, commercially available dome-shaped GaAs:Zn emitters with comparable power outputs degrade much less, and the degradation that is observed can be recovered by forward-bias-induced annealing. Further, this bias-induced recovery can be achieved by applying forward-current pulses only 10 to 50 ms in width. The lack of any bias-induced recovery in the GaAs:Si devices led to an investigation of gamma-induced deep levels using the transient capacitance method of deep level transient spectroscopy (DLTS). Following irradiation, two levels with thermal activation energies of 0.21 and 0.78 eV were observed. Subsequent forward bias reduced the concentration of the 0.21-eV level but had relatively little effect on the 0.78-eV level. These results suggest that the near midgap 0.78-eV level is one of the nonradiative recombination centers responsible for light output degradation.     

Doubly Passively Self-Q-Switched Cr4+:Nd3+:YAG Laser With a GaAs Output Coupler in a Short Cavity

By using a GaAs as both an output coupler and a saturable absorber, we present a doubly passively self-Q-switched Cr⁴⁺:Nd³⁺:YAG laser in a short cavity for the first time to our knowledge. This laser can generate more symmetric pulse shape and shorter pulsewidth in comparison with the solely self-Q-switched Cr⁴⁺:Nd³⁺:YAG laser. The output pulse energy and peak powers are higher than those in our previous doubly passively Q-switched lasers. By considering the Gaussian spatial distribution of the intra-cavity photon density and the free carrier absorption (FCA) in GaAs wafer, a set of modified rate equations have been introduced to describe the performances of the doubly Q-switched Cr ⁴⁺:Nd³⁺:YAG laser with GaAs coupler. The numerical solutions of the equations and the experimental results are found to agree with each other very well. The effect of FCA process in GaAs wafer has been discussed and proved to play an important role in the pulse compression and symmetry     

Characteristics and device applications of erbium doped III-V semiconductors grown by molecular beam epitaxy

We have studied the properties of molecular beam epitaxially (MBE)-grown Erdoped III-V semiconductors for optoelectronic applications. Optically excited Er³⁺ in insulating materials exhibits optical emission chiefly around 1.54 μm, in the range of minimum loss in silica fiber. It was thought, therefore, that an electrically pumped Er-doped semiconductor laser would find great applicability in fiber-optic communication systems. Exhaustive photoluminescence (PL) characterization was conducted on several of As-based III-V semiconductors doped with Er, on bulk as well as quantum-well structures. We did not observe any Errelated PL emission at 1.54 μm for any of the materials/structures studied, a phenomenon which renders impractical the realization of an Er-doped III-V semiconductor laser. Deep level transient spectroscopy studies were performed on GaAs and AlGaAs co-doped with Er and Si to investigate the presence of any Er-related deep levels. The lack of band-edge luminescence in the GaAs:Er films led us to perform carrier-lifetime measurements by electro-optic sampling of photoconductive transients generated in these films. We discovered lifetimes in the picosecond regime, tunable by varying the Er concentration in the films. We also found the films to be highly resistive, the resistivity increasing with increasing Er-concentration. Intensive structural characterization (double-crys-tal x-ray and transmission electron microscopy) performed by us on GaAs:Er epilayers indicates the presence of high-density nanometer-sized ErAs precipitates in MBE-grown GaAs:Er. These metallic nanoprecipitates probably form internal Schottky barriers within the GaAs matrix, which give rise to Shockley-Read-Hall recombination centers, thus accounting for both the high resistivities and the ultrashort carrier lifetimes. Optoelectronic devices fabricated included novel tunable (in terms of speed and responsivity) high-speed metal-semiconductor-metal (MSM) photodiodes made with GaAs:Er. Pseudomorphic AlGaAs/ InGaAs modulation doped field effect transistors (MODFETs) (for high-speed MSM-FET monolithically integrated optical photoreceivers) were also fabricated using a GaAs:Er buffer layer which substantially reduced backgating effects in these devices.     

Photorefractive determination of the sign of photocarriers in InP and GaAs

The sign of the majority photocarriers in semi-insulating iron-doped InP and undoped GaAs containing EL2 centres illuminated at 1.06 ?m is unambiguously determined from the direction of beam coupling in a two-wave photorefractive mixing experiment previously applied to ferroelectric crystals. Majority photocarriers in these InP:Fe and GaAs:EL2 crystals are found to be electrons.     

Screening of Oxide/GaAs Interfaces for MOSFET Applications

Photoluminescence intensity (PL-I) data are presented for 22 dielectric/GaAs systems investigated for MOSFET applications. The PL-I technique has been identified as a most useful and reliable tool for screening dielectric/GaAs interfaces and has been instrumental in the identification of a device quality dielectric/GaAs interface: in situ deposited $ hbox{Ga}_{2}hbox{O}_{3}$ on GaAs. The early discovery of such an interface has allowed us to focus resources and to succeed to manufacture GaAs MOSFETs which perform in line with theoretical model predictions after more than 40 years of failed attempts. It is strongly recommended to extend the technique to the investigation of CMOS relevant channel materials such as InGaAs.      

Anti-phase domain-free growth of GaAs on offcut (001) Ge wafers by molecular beam epitaxy with suppressed Ge outdiffusion

The nucleation and growth of GaAs films on offcut (001) Ge wafers by solid source molecular beam epitaxy (MBE) is investigated, with the objective of establishing nucleation conditions which reproducibly yield GaAs films which are free of antiphase domains (APDs) and which have suppressed Ge outdiffusion into the GaAs layer. The nucleation process is monitored by in-situ reflection high energy electron diffraction and Auger electron spectroscopy. Several nucleation variables are studied, including the state of the initial Ge surface (single-domain 2×1 or mixed-domain 2×1:1×2), the initial prelayer (As, Ga, or mixed), and the initial GaAs growth temperature (350 or 500°C). Conditions are identified which simultaneously produce APD-free GaAs layers several microns in thickness on Ge wafers with undetectable Ge outdiffusion and with surface roughness equivalent to that of GaAs/GaAs homoepitaxy. APD-free material is obtained using either As or Ga nucleation layers, with the GaAs domain dependent upon the initial exposure chemical species. Key growth steps for APD-free GaAs/Ge growth by solid source MBE include an epitaxial Ge buffer deposited in the MBE chamber to bury carbon contamination from the underlying Ge wafer, an anneal of the Ge buffer at 640°C to generate a predominantly double atomic-height stepped surface, and nucleation of GaAs growth by a ten monolayer migration enhanced epitaxy step initiated with either pure As or Ga. We identify this last step as being responsible for blocking Ge outdiffusion to below 10¹⁵ cm⁻³ within 0.5 microns of the GaAs/Ge interface.     

手机用GaAs SPDT开关的全离子注入技术

对移动通信用单刀双掷开关制作工艺中的 Ga As全离子注入技术进行了实验比较和讨论 ,认为 76mmGa As圆片经光片注入 Si离子后包封 40 nm Si O2 +60 nm Si N进行快速退火再进行 B离子注入隔离和器件制作的工艺方法先进、工艺简便、表面物理性能好、产品成本低、重复性和均匀性好、成品率高及器件性能优良。     

Effect of uniform compression on photoluminescence spectra of GaAs layers heavily doped with beryllium

The effect of high-temperature annealing at high hydrostatic pressures on photoluminescence of heavily doped GaAs:Be layers grown by molecular-beam epitaxy on GaAs substrates was studied. A blue shift of the band-edge luminescence line and an increase in the relative intensity of the shoulder at the high-energy wing of this line were detected after annealing in the spectra of layers with a beryllium atom concentration higher than 5×10¹⁹ cm^?3. The same layers featured a concentration-related decrease in the GaAs lattice parameter, which does not conform to the Vegard law. These effects can be attributed to the formation of beryllium inclusions in heavily doped GaAs. Due to different compressibility and thermal expansion coefficients of Be inclusions and GaAs, high-temperature and high-pressure treatment gives rise to structural defects; hence, the probability of transitions that are indirect in the k space increases.     

Field returns, a source of natural failure mechanisms

Reliability investigations and product qualifications are typically built on a set of “standard” aging methods which are designed to extract degradation that can be statistically analyzed in order to predict lifetimes. This study is intended to reveal information about what actually happens to devices during use by the customer as determined by failure analysis. This information is provided as an account of experiences with supplier-customer relationships It is intended to describe expectations (from the supplier viewpoint) and to guide aging and qualification methodologies towards meeting those expectations. Comparisons to accelerated aging results are discussed. This work was initiated to provide a modern update to a similar paper entitled: “GaAs IC Reliability Returns: A Story of Abuse”. The original data was presented at the 1992 GaAs REL Workshop on October 4, 1992 in Miami Beach, Florida [Roesch Bill, Rubalcava AL, Winters RA. GaAs IC reliability returns: a story of abuse. In: GaAs REL Workshop, October 4, 1992, Miami Beach, Florida. p. 30-4. [1]].