Properties of Au/W/GaAs Schottky barriers

The electrical and chemical properties of r.f. sputtered Au/W Schottky barriers on GaAs studied by Auger electron spectroscopy are reported. There is considerable interest in such work at present owing to the refractory nature and the thermal stability of tungsten on GaAs. The built-in potential of tungsten on GaAs was measured to be about 0.65 eV by both I–V and C–V techniques. Although tungsten alone has been reported to be stable on GaAs even at elevated temperatures of up to 500°C, the presence of a gold overlay and/or pinholes in the r.f. sputtered tungsten reduces its refractory nature. W/Au Schottky barriers annealed at 475 and 575°C for 10 min showed no appreciable degradation in their electrical properties. Samples annealed at 475°C for 2 h and 800°C for 15 min showed some degradation and migration of gold through the tungsten film. GaAs field effect transistors (FETs) with tungsten gates 0.7 μm long showed a maximum measured gain of 14 dB at 8 GHz.     

Reliability investigation of implanted microwave InGaP/GaAs HBTs

In this paper, we report the fabrication and characterisation of C-doped InGaP/GaAs microwave HBTs using a planar self-aligned technology based on O⁺/H⁺ or O⁺/He⁺ implant isolation schemes. We observed current gain variations with emitter/base geometries in the H⁺ implanted HBTs while no such variation was observed in the He⁺ implanted transistors. This latter phenomenon is characterised by a current gain increase in the smaller device and this was attributed to a decrease of the hole concentration in the base, caused by the formation of C---H complexes in the C-doped GaAs base region. We therefore recommend the use of O⁺/He⁺ implant scheme for the fabrication of reliable high performance C-doped base HBTs.     

Photoluminescence characterization of InGaP/GaAs/InGaP quantum wires

We investigated the photoluminescence of InGaP/GaAs/InGaP heterostructures with the aim to prepare quantum wires by the epitaxial overgrowth of V-groove patterned substrates. Planar and V-groove patterned GaAs semiinsulating substrates were used for epitaxial growth in a low-pressure MOVPE equipment with a horizontal reactor. Low temperature photoluminescence measurements show that the composition of the InGaP ternary compound prepared on the patterned substrates is shifted to a higher InP mole fraction compared with the planar ones. On the other hand, the measurement on the V-grooved samples showed that the PL peak is shifted to higher energies (i.e. to the higher amount of Ga), which indicates a change in the ternary composition of about 5%. Crystalline quality of the overgrown structures was studied by transmission electron microscopy. Both, photoluminescence and photoluminescence polarization measurement show that quantum wires can be successfully prepared in the InGaP/GaAs/InGaP system.     

Microstructural analysis of Pd/Pt/Au/Pd ohmic contacts to InGaP/GaAs

Microstructural evolution during the annealing of Pd/Pt/Au/Pd p-ohmic contacts (with and without a thin layer of Zn) to InGaP/GaAs HBTs has been studied using transmission electron microscopy (TEM). Metal layers were deposited by electron beam evaporation directly onto the InGaP emitter layer with the intention of consuming the InGaP during annealing to contact the heavily C-doped p-type GaAs (3×10¹⁹ cm⁻³) base layer below. Initial reaction between Pd and Pt and InGaP formed a five-component amorphous layer (Pd, Pt, In, Ga and P), which crystallized to (Pt_xPd_1−x)5(In_yGa_1−y)P (0≤x, y≤1) at the interface between Pt and the amorphous layer. Annealing at temperatures ≥415°C caused complete decomposition of the InGaP and partial decomposition of the GaAs base layer, producing a contact consisting of (Pt_xPd_1−x)5(In_yGa_1−y)P, PtAs₂ and PdGa. The attainment of low contact resistances did not depend on the presence of Zn. Minimum values of 0.10−0.12 Ω mm were achieved after annealing at 415–440°C for contacts both with and without Zn. This revised version was published online in July 2006 with corrections to the Cover Date.     

Features of current flow in structures based on Au/Ti/n-InAlAs Schottky barriers

Current–voltage (I–V) characteristics of Au/Ti/n-InAlAs/InP Shottky barriers have been studied in a temperature range of 100–380 K. It is established that, as the temperature increases from 100 to 200 K, the ideality factor drops from 1.58 to 1.1, while the barrier height grows from 0.55 to 0.69 eV. With a subsequent temperature increase from 200 to 380 K, both the ideality factor and barrier height vary, but only weakly. This behavior agrees well with the model of lateral inhomogeneity of the barrier height (Tung model), which is confirmed by the linear dependence of the barrier height on the ideality factor at temperatures within 100–200 K. Calculations according to this model yielded the value of 0.88 eV for the homogeneous-junction barrier height, 10^–4 cm^2/3 V^1/3 for the mean-square deviation of the Gaussian distribution of barrier heights, 3.7 × 10^–11 cm² for the effective area of regions with reduced barrier heights, and 10.7 A cm^–2 K^–2 for the Richardson constant.

     

GaAs/InGaP异质界面的湿法腐蚀

对柠檬酸系、盐酸系溶液腐蚀GaAs/InGaP异质结构材料体系时出现的腐蚀不均匀现象进行了实验研究,采用原子力显微镜(AFM)、电子显微镜、台阶仪等分析了不同腐蚀条件下GaAs/InGaP异质界面的腐蚀形貌,找到了简单有效的办法,可获得很好的表面平整度,同时侧向腐蚀也较小.     

Characteristics of Pd/InGaP Schottky diodes hydrogen sensors

Pd/InGaP hydrogen sensors based on the metal-oxide-semiconductor (MOS) and metal-semiconductor Schottky diodes have been fabricated and systematically studied. The effects of hydrogen adsorption on device performances such as the current-voltage characteristics, barrier height variation, hydrogen coverage, and heat of adsorption are investigated. The studied devices exhibit very wide hydrogen concentration detection regimes and remarkable hydrogen-sensing properties. Particularly, an extremely low hydrogen concentration of 15 ppm H/sub 2//air at room temperature can be detected. In addition, under the presence of oxide layers in the studied MOS device structure, the enhancements of barrier height and high-temperature operating capability are observed. The initial heat of adsorption for Pd/oxide and Pd/semiconductor interface are calculated as 355 and 65.9 meV/atom, respectively. Furthermore, the considerably short response times are found in studied devices.     

InGaP/GaAs外延材料合金有序度的表征

对InGaP/GaAs外延材料合金有序度表征方法进行了综述，指出从结构X-Ray）光学性能摘要（透射电子显微镜，、（光、电学性能三方面度量InGaP/GaAs材料的有序度。     

一种具有GaInAsN/GaAs量子阱结构的三结太阳能电池的设计

该文使用传输矩阵法分析了GaInAsN/GaAs量子阱对电子的透射情况,并使用crosslight软件对GaInAsN/GaAs量子阱太阳能电池的伏安特性进行了数值模拟和分析。初步讨论了量子阱的阱宽和垒厚的变化对量子阱电池伏安特性的影响.模拟结果发现垒厚32nm、阱宽7nm的量子阱光伏性能表现良好。作为有源区,当将该量子阱加入到GaAs子电池中,InGaP/GaAs/Ge三结电池在AM0下的短路电流密度达到19.81mA/cm2,比未使用量子阱有源区的三结电池提高了20%。     

Electrical and microstructural investigation of Au/Pd/ri ohmic contacts for AIGaAs/GaAs heterojunction bipolar transistors

Abstract

The microstructure and electrical properties of as deposited and annealed Au (400 nm)/Pd (75 nm)/Ti (10 nm) contact structures to p type GaAs, C doped with a concentration of 5 × 10¹⁸ and 5 × 10¹⁹ cm^?3, have been investigated using transmission electron microscopy, and current-voltage measurements as afunction of temperature in the range 198–348 K. The specific contact resistivities have also been measured using the transmission line method. It was found that increasing the epilayer doping level by an order of magnitude, from 5 × 10¹⁸ to 5 × 10¹⁹ cm^?3, caused the dominant current transport mechanism to change from thermionic field emission to field emission. For the lower level doped epilayers generationrecombination within the depletion region was found to be the dominant current transport mechanism for temperatures below 289 K. The contacts to the more highly doped epilayers (C doped, 5 × 10¹⁹ cm^?3) had specific contact resistivities of 0·08 ± 0·03 Ωmm and 0·05 ± 0·06 Ωmm, respectively. These values, together with a minimal metal penetration in the semiconductor of <15 nm, indicate that these contacts are suitable for heterojunction bipolar device applications.

MST/3325     

四结太阳能电池InGaP/GaAs/GaInAsN/Ge的设计与模拟

随着多结太阳能电池技术的发展,追求更高效率的四结太阳能电池结构InGaP/GaAs( In-GaAs)/(新材料)/Ge受到广泛的研究.四元化合物材料Ga1-xInxAs1-yNy通过控制其组分比例,其禁带宽度可以调整为0.95ev - 1.05ev,并且可以与GaAs,Ge实现晶格匹配,是应用于新一代太阳能电池最有潜...     

Electrical transport characteristics of Au/n-GaN Schottky diodes

The current–voltage measurements were performed in the temperature range (80–300 K) on Au/ n-GaN Schottky barrier type diodes. The Schottky diode shows non-ideal I(V_G) behaviour with ideality factors n equals to 1.18 and 1.81 at 300 K and 80 K, respectively, and are thought to have a metal-interface layer-semiconductor configuration. Under forward bias and for T ≥ 200 K, the electrical current transport was controlled by the thermionic emission (TE) process. However, for T ≤ 200 K, The current was controlled by the thermionic field emission (TFE). The characteristic energy E₀₀ = 3.48 meV was obtained from the I(V_G, T) measurements and agreed very well with the value of E₀₀ = 3.62 meV calculated theoretically. The zero-bias barrier height ϕ_B0 determined from the I(V_G) measurements was 0.84 eV at 300 K and decreases to 0.49 eV at 80 K.     

Controlling the wavelength of InGaAs/GaAs/InGaP lasers by ion implantation

The possibility of controlling the wavelength of emission from an InGaAs/GaAs/InGaP laser heterostructure with strained quantum wells (QWs) using medium-energy proton implantation followed by thermal annealing has been studied. It is established that the optimum proton energy is related to the arrangement of QWs in the structure (e.g., 150 keV for QWs at a depth of ≈1.3 μm). Proton irradiation to a total dose of 6 × 10¹⁴ cm⁻² followed by annealing at 700°C allows the wavelength of emission from the modified region to be decreased by 8–10 nm at minimum losses in the output intensity. The observed effect can be used to obtain two-band emission from the same chip and has good prospects for use in the development of new optoelectronic schemes.     

Effect of strong illumination on current-voltage characteristics of Au/Si, Al/Si and Sn/Si Schottky barriers with native oxide layer

Light induced general degradation in the dark I–V characteristics of Au/Si, Al/Si and Sn/Si junctions at low temperature and at room temperature. Illumination caused changes in the interface and bulk properties of the investigated junctions, all of them prepared under identical conditions. Their barrier heights, φB change with increasing illumination time. The largest rate of degradation in φB upon exposure to light was observed for an Sn/Si junction (lowest φB), whereas the smallest change occurred with an Au/Si junction (highest φB). At low temperature, upon turning off the light, the photogenerated current of the Sn/Si sample exhibited faster recovery in reaching the initial dark current (at till=0) than the Al/Si junction; for the less reactive Au/Si sample, the presence of the oxide layer reduced the leakage current and subsequently delayed recovery of the measured photocurrent. This revised version was published online in August 2006 with corrections to the Cover Date.     

InGaP/GaAs HBT费米统计律下的数值模拟计算

用费米分布函数对HBT结构中载流子的分布进行了计算,与常用的玻尔兹曼统计律得到的载流子分布进行了比较分析。同时在热场发射－扩散模型的基础上,用两种方法得到的载流子分布分别对InGaP/GaAsHBT进行了数值模拟计算和分析。     

RBS-C and ellipsometric investigations of radiation damage in hot-implanted GaAs layers

Semi-insulating (1 0 0) GaAs single crystalline substrates have been doubly Al⁺-implanted using ion beams of the 250 keV energy and the fluence F = 3.5 × 10¹⁶ cm⁻², and 100 keV with F = 9.6 × 10¹⁵ cm⁻² at six target temperatures ranging from 250 to 500 °C. The radiation damage introduced by such “hot implantation” was subsequently investigated by Rutherford Backscattering Spectrometry with Channeling (RBS-C) and Variable Angle Spectroscopic Ellipsometry (VASE) techniques. Using these experimental methods we determined a degree of lattice disorder. With the increasing implantation temperature the degree of disorder substantially decreases. No evidence of full amorphization of the implanted GaAs layers has been found in the present studies. The results of non-destructive ellipsometric characterization are in good agreement with the RBS-C investigations.     

Integrated a ZnSe MSM Photodiode and an InGaP/GaAs HBT on a GaAs Substrate for High Sensitivity Short Wavelength Photodetector

A ZnSe MSM photodiode and an InGaP/GaAs HBT have been integrated successfully on a GaAs substrate by use of the selective-area epitaxy technique. The optical and electrical characterizations of the integrated photoreceiver as well as individual components used in this device structure were estimated. Photocurrent induced from the metal-semiconductor-metal (MSM) photodiode was amplified linearly by a common-emitter circuit composed of a HBT. A current amplification ratio and a voltage amplification sensitivity of the integrated device measured in this work were 20.8 and ${-}29.6$ mV/$mu$ W, respectively. The result does not only demonstrate the high sensitivity monolithic photoreceiver but indicates the potential of the selective-area epitaxy technique in the development of WBG-based short wavelength integrated devices.      

Annealing study of InGaP/GaAs heterojunction bipolar transistor and carbon-doped pGaAs base layers

In this work we have examined the effect of RF annealing (450–750°C, 5–30 min) upon both InGaP/GaAs-based hetero-junction bipolar transistor (HBT) structures, fabricated by metalorganic vapour phase epitaxy (MOVPE), as well as thick carbon (C)-doped p⁺GaAs HBT base layers with varying layer thickness, dopant level and type (intrinsic and extrinsic C precursors) and co-doping (In) strain compensation. Anneal-induced changes in the p⁺GaAs layer lattice strain, Hall carrier concentration and mobility were compared with non-radiative losses, determined from photoluminescence (PL) intensity data. Majority and minority carrier property differences were also compared with IR reflection, Raman backscattering and photoreflectance (PR) data and correlated with changes in MOVPE hydrogen background concentration as determined by secondary-ion-mass-spectroscopy (SIMS). Thick base layer (1.3 μm) HBT structures were also examined for different anneal temperatures and time, showing significant changes in the PR emitter(InGaP)/base (p⁺GaAs) and base/collector (n-GaAs) interface regions for the 650°C anneal condition, as correlated with both PL and SIMS hydrogen concentration data.     

InGaP/GaAs微波HBT器件与电路研究及应用进展

概述了近年来微波InGaP/GaAs异质结双极晶管(HBT)器件和集成电路的研究和应用现状,着重阐述了HBT器件的热设计、降低偏移电压、离子注入隔离、湿法腐蚀,以及用于电路设计的等效电路模型等关键问题.