MBE生长InGaAs/In_(0.32≤x≤0.52)Al_(1-x)As MM-HEMT材料

在GaAs衬底上利用分子束外延技术生长了不同In组分的MetamorphicHEMT(简称MM-HEMT)。通过对MM-HEMT材料中台阶式缓冲层材料种类、台阶宽度、初始组分以及生长温度等生长参数、生长条件和结构参数进行优化,得到了具有良好电学性能的MM-HEMT材料,其二维电子气迁移率和浓度指标与国外同期水平相当。     

InP基RTD/HEMT集成的几个关键工艺研究

用MBE设备在半绝缘的InP衬底上依次生长高电子迁移率晶体管(HEMT)外延材料和共振遂穿二极管(RTD)外延材料,在此材料结构基础上研究和分析了RTD与HEMT器件单片集成工艺中的隔离工艺、欧姆接触工艺、HEMT栅挖槽工艺和空气桥工艺等几步关键工艺,给出了这些工艺的相关参数。利用上述工艺成功地制作了RTD和HEMT器件,并在室温下分别测试了RTD器件和HEMT器件的电学特性。测试表明:在室温下,RTD器件的峰电流密度与谷电流密度之比(PVCR)为3.66;HEMT器件的最大跨导约为370 mS/mm,在Vds=1.5 V时的饱和电流约为391 mA/mm。这将为RTD与HEMT的单片集成研究奠定工艺基础。     

AlGaN/GaN HEMT器件工艺的研究进展

首先论述了Al GaN/GaN高电子迁移率晶体管(HEMT)在微波大功率领域的应用优势和潜力;其次,介绍并分析了影响Al GaN/GaN HEMT性能的主要参数,分析表明要提高Al-GaN/GaN HEMT的频率和功率性能,需改善寄生电阻、电容、栅长和击穿电压等参数。然后,着重从材料结构和器件工艺的角度阐述了近年来Al GaN/GaN HEMT的研究进展,详细归纳了目前主要的材料生长和器件制作工艺,可以看出基本的工艺思路是尽量提高材料二维电子气的浓度和材料对二维电子气的限制能力的同时减小器件的寄生电容和电阻,增强栅极对沟道的控制能力。另外,根据具体情况调节栅长及沟道电场。最后,简要探讨了Al GaN/GaN HEMT还存在的问题以及面临的挑战。     

HEMT集成电压比较器

本文从HEMT器件的基本结构、工作机理入手,对HEMT器件的设计进行了探讨。根据实际HEMT器件I-V特性曲线,建立了实际工艺条件下HEMT器件I-V特性计算模型。利用该模型对CML集成电压比较器进行模拟分析,确定了元件各种电参数及结构参数。采用离子注入技术进行器件的隔离,分别用HEMT和PHEMT材料,研制出了增强型、低功耗集成电压比较器,在1GSPS取样速率时,电压分辨率为30mV,功耗为27mW。     

AlGaN/GaN HEMT材料外延技术研究

采用低压MOCVD技术在蓝宝石和SiC衬底上生长了本征GaN和AlGaN/GaN HEMT结构材料。生长过程中采用了EpiTUNEⅡ在位监测技术,对材料生长工艺进行了模型分析以及优化控制。在获得具有良好表面形貌、晶体质量以及光荧光谱的GaN本征材料基础上,生长了AlGaN/GaN HEMT结构材料,获得了良好的2DEG性能。     

增强型AlGaN/GaN HEMT器件工艺的研究进展

随着高压开关和高速射频电路的发展,增强型GaN基高电子迁移率晶体管(HEMT)成为该领域内的研究热点。增强型GaN基HEMT只有在加正栅压才有工作电流,可以大大拓展该器件在低功耗数字电路中的应用。近年来,国内外对增强型GaN基HEMT阈值电压的研究主要集中以下两个方面:在材料生长方面,通过生长薄势垒、降低Al组分、生长无极化电荷的AlGaN/GaN异质材料、生长InGaN或p-GaN盖帽层,来控制二维电子气浓度;在器件工艺方面,采用高功函数金属、MIS结构、刻蚀凹栅、F基等离子体处理,来控制表面电势,影响二维电子气浓度。从影响器件阈值电压的相关因素出发,探讨了实现和优化增强型GaN基HEMT的各种工艺方法和发展方向。     

调制掺杂低噪声器件

制造了0.4μm×250μm栅赝配AlGaAs-InGaAs HEMT。器件具有比良的高频、低噪声特性。赝配材料采用分子束外延生长。本文介绍了器件结构、性能并讨论了沟道电子的平均速度。     

Si基GaN材料寄生导电层的研究

通过对Si基GaN材料的电学性能进行测量分析,确认了该材料体系所特有的寄生导电层现象。研究了寄生导电层对Si基GaN高电子迁移率晶体管(HEMT)微波功率性能和击穿性能的不良影响。通过材料生长工艺的优化,降低了寄生导电层的导电性,获得了击穿电压超过320V的Si基GaN HEMT功率电子器件。     

InP-HEMT中复合沟道的设计与生长

设计并生长了带有复合沟道的InP基HEMT材料,该材料具有较高的二维电子气浓度和迁移率。在使用In_xGa_(1-x)As/In_(0.53)Ga_(0.47)As复合沟道时,当In组分等于0.7时得到较好的沟道输运性能;在使用InAs复合沟道时,得到了二维电子气浓度为2.3×10~(12)/cm~2、室温迁移率高达13600 cm~2/V·s的性能优良的HEMT材料。     

RF-MBE生长的高Al势垒层AlGaN/GaN HEMT结构

采用RF-MBE技术,在蓝宝石衬底上生长了高Al组分势垒层AlGaN/GaN HEMT结构.用三晶X射线衍射分析得到AlGaN势垒层的Al组分约为43%,异质结构晶体质量较高,界面比较光滑.变温霍尔测量显示此结构具有良好的电学性能,室温时电子迁移率和电子浓度分别高达1246cm2/(V·s)和1.429×1013cm-2,二者的乘积为1.8×1016V-1·s-1.用此材料研制的器件,直流特性得到了提高,最大漏极输出电流为1.0A/mm,非本征跨导为218mS/mm.结果表明,提高AlGaN势垒层Al的组分有助于提高AlGaN/GaN HEMT结构材料的电学性能和器件性能.     

Metamorphic In0.4Al0.6As/In0.4Ga0.6As HEMTs on GaAs substrate

New In_0.4Al_0.6As/In_0.4Ga_0.6 As metamorphic (MM) high electron mobility transistors (HEMTs) have been successfully fabricated on GaAs substrate with T-shaped gate lengths varying from 0.1 to 0.25 μm. The Schottky characteristics are a forward turn-on voltage of 0.7 V and a gate breakdown voltage of -10.5 V. These new MM-HEMTs exhibit typical drain currents of 600 mA/mm and extrinsic transconductance superior to 720 mS/mm. An extrinsic current cutoff frequency f_T of 195 GHz is achieved with the 0.1-μm gate length device. These results are the first reported for In_0.4 Al_0.6As/In_0.4Ga_0.6As MM-HEMTs on GaAs substrate     

Enhancement mode metamorphicAl0.67In0.33As/Ga0.66In0.34As HEMT on GaAs substrate with high breakdown voltage

This paper presents original and experimental results provided by E-mode Al_0.67In_0.33As/Ga_0.66In_0.34 As metamorphic HEMT. The devices exhibit good dc and rf performances. The 0.4 μm gate length devices have saturation current density of 355 mA/mm at +0.6 V gate-to-source voltage. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -16 V. It is the first time, to our knowledge, that gate current issued from impact ionization have been observed in these devices versus gate to drain extension. These results are the first reported for E-mode Al _0.67In_0.33As/Ga_0.66In_0.34As MM-HEMTs on GaAs substrate     

基于MBE替代硅衬底的材料综述

主要介绍了几种用MBE技术生长HgCdTe/CdTe的Si衬底的替代性衬底材料的基本参数,以及不同材料的最新生长过程及结果,和对它们的生长结果的比较分析,以此来选择较为适合替代Si衬底来生长HgCdTe/CdTe的衬底。本文通过一系列的对比,得出目前最有发展前景的替代衬底是GaSb衬底,是未来发展的方向。     

激光增进的半导体异质结外延生长

文章阐述了光辅助外延生长的基本原理,光辐射增强生长速率主要有：光分解、光催化和光的热分解三种机制;介绍其在半导体材料外延生长中的具体应用,包括降低温度、掺杂控制、原子层外延和选择性外延;分析了实验中光的作用以及对材料晶体质量和光电特性的影响,为生长高质量材料提供实验基础。     

Engineered materials were driven by the industrial evolution

This article deals with the demands for materials with assured properties, fostered investigations and the growth of scientific knowledge, towards the end of the 19th century. The efforts during these eras provided the impetus for the emergence and growth of engineered materials, including many different polymers (plastics), non-crystalline metals, and stronger than steel fibers, such as carbon fibers. Process engineers created processes and plants that required instrumentation to produce these new materials consistently.     

Recent Progress on 1.55- μm Dilute-Nitride Lasers

We review the recent developments in GaAs-based 1.55-mum lasers grown by molecular beam epitaxy (MBE). While materials growth is challenging, the growth window appears to be relatively broad and is described in detail. The key considerations for producing high-quality GalnNAsSb material emitting at 1.55-mum regime are examined, including the nitrogen plasma conditions, ion removal from the nitrogen flux, surfactant- mediated growth, the roles of various V-II ratios, the growth temperature, the active region thermal budget, proper annealing, and composition. We find that emission may be tuned throughout the 1.55-mum communications band without penalty to the optical quality varying only one parameter - the total growth rate. This powerful result is validated by the demonstration of low-threshold edge-emitting lasers throughout the 1.55-mum regime, including threshold current densities as low as 318 A/cm² at 1.54 mum. Additional characterization by Z-parameter techniques, cavity length studies, and band offset measurements were performed to better understand the temperature stability of device performance. Lasing was extended as far as 1.63 mum under nonoptimized growth conditions. The GaAs-based dilute-nitrides are emerging as a very promising alternative to InP-based materials at 1.55-mum due to their high gain, greater range of achievable band offsets, as well as the availability of lattice-matched AlAs-GaAs materials and native oxide layers for vertical-cavity surface-emitting lasers (VCSELs). Indeed, this effort has enabled the first electrically injected C-band VCSEL on GaAs.     

分子束外延InAlSb/InSb晶体的质量研究

InAlSb/InSb薄膜材料的晶体质量会直接影响器件的性能。提高薄膜材料的晶体质量可以有效降低器件的暗电流,提高探测率和均匀性等。主要报道了掺铝锑化铟分子束外延技术的初步研究结果。通过采用多种测试方法对InAlSb分子束外延膜的晶体质量进行了分析,找出了影响晶体质量的因素,提高了InAlSb分子束外延的技术水平。实验结果表明,通过优化生长温度、束流比、升降温速率以及退火工艺等生长条件,可以获得高质量的InAlSb分子束外延膜。     

Non-hydride group V sources for OMVPE

A major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of III/V semiconductor materials is the hazard posed by the hydride sources, AsH₃ and PH₃, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the highest quality materials. The ideal group V source would be a nontoxic liquid with a moderate vapor pressure (50-500 Torr). To be suitable for OMVPE growth, the molecule must pyrolyze at ordinary growth temperatures, be stable against decomposition in the bottle at room temperature, and not participate in undesirable parasitic reactions with the group III source molecules. The new sources have additional constraints related to purity. They must be easily purified without decomposing and produce no detectable carbon contamination in the resultant epitaxial layers. This set of stringent requirements eliminates most commonly available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire area of group V sources, including the elemental sources, for OMVPE growth of III/V materials will be reviewed. The sources with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give unacceptably high carbon incorporation. Diethylarsine, which has one H attached to the As, produces high quality GaAs but has an inconveniently low vapor pressure. Trimethylphosphine and triethylphosphine o not pyrolyze at low enough temperatures to be useful for conventional OMVPE growth. Tertbutylarsine (TBAs) and tertbutylphosphine (TBP) appear to be promising source materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures than for PH₃, allowing the use of low values of V/III ratio for the growth of high quality material. No carbon contamination can be attributed to the TBP. Control of the As/P ratio in OMVPE grown GaAsP is much improved for TBP as compared with PH₃ due to the more rapid pyrolysis. At normal growth temperatures the P distribution coefficient is nearly unity. TBAs has been less studied, but appears to have similar attributes including a favorable vapor pressure and lower pyrolysis temperature than AsH₃, allowing OMVPE growth of GaAs at low values of V/III ratio. The substitution of TBAs for AsH₃ results in no observable increase in carbon in the epitaxial GaAs.     

Atmospheric and low pressure shadow masked MOVPE growth of InGaAs(P)/InP and (In)GaAs/(Al)GaAs heterostructures and quantum wells

The shadow masked growth technique is presented as a tool to achieve thickness and bandgap variations laterally over the substrate during metalorganic vapor phase epitaxy. Lateral thickness and bandgap variations are very important for the fabrication of photonic integrated circuits, where several passive and active optical components need to be integrated on the same substrate. Several aspects of the shadow masked growth are characterized for InP based materials as well as for GaAs based materials. Thickness reductions are studied as a function of the mask dimensions, the reactor pressure, the orientation of the masked channels and the undercutting of the mask. The thickness reduction is strongly influenced by the mask dimensions and the reactor pressure, while the influence of the orientation of the channels and the amount of undercutting is only significant for narrow mask windows. During shadow masked growth, there are not only thickness variations but also compositional variations. Therefore, we studied the changes in In/Ga and As/P ratios for InGaAs and InGaAsP layers. It appears that mainly the In/Ga-ratio is responsible for compositional changes and that the As/P-ratio remains unchanged during shadow masked growth.