GaN材料的GSMBE生长

在国内首次用ＮＨ３作氮源的ＧＳＭＢＥ方法在α－Ａｌ２Ｏ３衬底上生长出了ＧａＮ单昌外延膜。ＧａＮ生长速率可达０．５μｍ／ｈ。ＧａＮ外延膜的（０００２）双晶Ｘ射线衍射峰回摆曲线的半高宽最窄为８ａｒｃｍｉｎ。霍尔迁移率为５０ｃｍ＾２／Ｖ．ｓ。对质量好的ＧａＮ膜，室温阴性发光谱上只有一个强而锐的近岸边发光峰，谱峰位于３７２ｎｍ处，谱峰半高宽为１４ｎｍ（１２５ｍｅＶ）。     

高迁移率AlGaN-GaN二维电子气

用金属有机物气相外延方法在（０００１）蓝宝石衬底上生长了ＡｌｘＧａ１－ｘＮ／ＧａＮ二维电子气结构。Ａｌ０．１３Ｇａ０．８７Ｎ（７００ｎｍ）／ＧａＮ（６００ｎｍ）异质结的室温电子迁移率达１０２４ｃｍ＾２／Ｖｓ,而ＧａＮ体材料的室温电子迁移率为３９０ｃｍ＾２／Ｖｓ;该异质结的７７Ｋ电子迁移率达３５００ｃｍ＾２／Ｖｓ,而ＧａＮ体材料的电子迁移率在１８５Ｋ下达到峰值,为４９０ｃｍ＾２／Ｖｓ,７７Ｋ下下降到     

NH3-MBE生长极化场二维电子气材料

介绍了用ＮＨ３－ＭＢＥ技术在蓝宝石Ｃ面上外延的高质量的ＧａＮ单层膜以及ＧＮ／ＡｌＮ／ＧａＮ极化感应二维电子气材料。外延膜都是Ｎ面材料。形成的二维电子气是“倒置二维电子气”。ＧａＮ单层膜的室温电子迁移率为３００ｃｍ＾２／Ｖｓ。二维电子气材料的迁移率为６８０ｃｍ＾２／Ｖｓ（ＲＴ）和１７００ｃｍ＾２／Ｖｓ（７７Ｋ）,相应的二维电子气的面密度为３．２＊１０＾１３ｃｍ＾－２（ＲＴ）和２．６ｘ１０＾１３ｃｍ＾     

p~＋－GaInAsSb／p－GaInAsSb／n－GaSb异质结红外控测器

ＧａＩｎＡｓＳｂ是红外探测器中重要的半导体材料之一。我们用水平常压金属氧化物化学气相淀积（ＭＯＣＶＤ）技术在ｎ型ＧａＳｂ衬底上成功地生长了ＧａＩｎＡｓＳｂ外延层，用ＰＬ谱、红外吸收谱、Ｘ射线衍射和扫描电子超声显微镜（ＳｃａｎｎｉｎｇＥｌｅｃｔｒｏｎＡｃｏｕｓｔｉｃＭｉｃｒｏｓｃｏｐｙ，ＳＥＡＭ）等实验手段对ＧａＩｎＡｓＳｂ外延层进行了表征。用ＧａＩｎＡｓＳｂ材料制作的红外探测器的光谱响应的截止波长达２．４μｍ，室温探测率Ｄ＊达１×１０９ｃｍＨｚ（１／２）／Ｗ，２．２５μｍ波长时的量子效率为３０％。本文首次给出了ＧａＩｎＡｓＳｂ外延层的扫描电子超声显微镜像（ＳＥＡＭ像），为扫描电子超声显微镜在半导体材料方面的应用开辟了一个新的领域。     

InGaN/AlGaN双异质结蓝光和绿光发光二极管

报道了用ＬＰ－ＭＯＶＰＥ技术在蓝宝石衬底上生长出以双掺Ｚｎ和Ｓｉ的ＩｎＧａＮ为有源区的蓝光和绿光ＩｎＧａＮ／ＡｌＧａＮ双异质结结构,并研制成功发射波长分别为４３０－４５０ｎｍ和５２０－５４０ｎｍ的蓝光和绿光ＬＥＤ。据查,这是国内首次有关六方ＧａＮ基绿光ＬＥＤ的报道。     

δ－掺杂GaAs／AlxGa_（1－x）As二维电子气结构材料的GSMBE生长与特性

本文用ＧＳＭＢＥ技术生长纯度ＧａＡｓ和δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ结构二维电子气材料并对其电学性能进行了研究。对于纯度ＧａＡｓ的ＧＳＭＢＥ生长和研究，在低掺Ｓｉ时，载流子浓度为２×１０~（１４）ｃｍ~（－３），７７Ｋ时的迁移率可达８４，０００ｃｍ~２／Ｖ．ｓ。对于用ＧＳＭＢＥ技术生长的δ－掺杂ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料，在优化了材料结构和生长工艺后，得到了液氮温度和６Ｋ迁移率分别为１７３，５８３ｃｍ~２／Ｖ．５和７．６７×１０~５ｃｍ~２／Ｖ．ｓ的高质量ＧａＡｓ／Ａｌ_ｘＧａ_（１－ｘ）Ａｓ二维电子气材料。     

碳掺杂GaAs的MBE生长

本文在国内首次采用自行设计的碳纤维束源炉及固态源ＭＢＥ技术生长了优质碳掺杂ＧａＡｓ、ＡｌＧａＡｓ及δ碳掺杂ＧａＡｓ外延层。获得了空穴浓度从４×１０１４ｃｍ－３到２×１０１９ｃｍ－３的ＧａＡｓ材料。用霍尔效应测量仪、电化学ＣＶ剖面仪和Ｘ射线双晶衍射仪分析了外延层的质量。用Ｎｏｍａｒｓｋｉ干涉显微镜和原子力显微镜分析了ＧａＡｓ的生长过程。结果表明碳是ＧａＡｓＩＩＶ族化合物半导体的极好的ｐ型掺杂剂。     

RF Plasma MBE生长GaN材料及特性研究

用ＲＦＰｌａｓｍａ ＭＢＥ方法生长出了ＧａＮ 材料,它的Ｘ 射线衍射半峰宽为３３５ 秒,７７Ｋ 下ＰＬ发光峰半峰宽为２２ｍｅＶ,表明了材料具有较高的晶体质量。根据Ｘ射线衍射分析,位错密度约为７ ．３ ×１０８ｃｍ －２ 。用Ｓｉ 作为掺杂剂,所得载流子浓度可覆盖１０１７ － １０１９ｃｍ －３ 的范围。掺Ｓｉ ＧａＮ 的ＰＬ谱表明,Ｓｉ 的引入可提高材料的发光效率。     

α－Al_2O_3衬底上生长的GaN膜的光学性质

采用金属有机化学气相淀积（ＭＯＣＶＤ）方法生长了α－Ａｌ２Ｏ３衬底上外延的高质量的单晶ＧａＮ薄膜。Ｘ射线衍射光谱与喇曼散射光谱表征了ＧａＮ外延薄膜的单晶结构和单晶质量。透射光谱和光调制反射光谱定出了六角单晶ＧａＮ薄膜的直接带隙宽度和光学参数。     

n型GaSb,InGaAsSb的MBE生长和特性研究

本文报导了非故意掺杂ＩｎＧａＡｓＳｂ本底浓度的降低和掺Ｔｅｎ型ＧａＳｂ和ＩｎＧａＡｓＳｂ的ＭＢＥ生长与特性的研究结果。结果表明，通过生长工艺的优化，ＧａＳｂ和ＩｎＧａＡｓＳｂ的背景空穴浓度可分别降至１．１×１０~（１６）ｃｍ~（－３）和４×１０~（１６）ｃｍ~（－３），室温空穴迁移率分别为９４０ｃｍ２／ｖ．ｓ和２６０ｃｍ~２／ｖ．ｓ。用Ｔｅ作ｎ型掺杂剂，可获得载流子浓度在１０~（１６）～１０~（１８）ｃｍ~（－３）的优质ＧａＳｂ和ＩｎＧａＡｓＳｂ外延层，所研制的材料已成功地制备出Ｄ_λ~＊＝４×１０~（１０）ｃｍＨｚ~（１／２）／Ｗ的室温ＩｎＧａＡｓＳｂ红外探测器和室温脉冲ＡｌＧａＡｓＳｂ／ＩｎＧａＡｓＳｂ双异质结激光器。     

GaN Electronics

An overview is presented of progress in GaN electronic devices for high‐power, high‐temperature applications. The wide bandgaps of the nitride materials, their excellent transport properties, and the availability of heterostructures (e.g., GaN/AlGaN) make them ideal candidates for these applications. In the past few years a wide range of devices have been reported, including heterostructure field effect transistors (HFETs), heterojunction bipolar transistors (HBTs), bipolar junction transistors (BJTs), Schottky and p–i–n rectifiers, and metal–oxide–semiconductor field effect transistors (MOSFETs). Some of the unexpected features of GaN‐based electronics include the ability to use piezoelectrically induced carriers for current transport in heterostructures and the sensitivity of the GaN surface to preferential loss of nitrogen during device processing.     

Preparation and optimization of freestanding GaN using low-temperature GaN layer

In this work, a method to acquire freestanding GaN by using low temperature (LT)-GaN layer was put forward. To obtain porous structure and increase the crystallinity, LT-GaN layers were annealed at high temperature. The morphology of LT-GaN layers with different thickness and annealing temperature before and after annealing was analyzed. Comparison of GaN films using different LT-GaN layers was made to acquire optimal LT-GaN process. According to HRXRD and Raman results, GaN grown on 800 nm LT-GaN layer which was annealed at 1090 °C has good crystal quality and small stress. The GaN film was successfully separated from the substrate after cooling down. The self-separation mechanism of this method was discussed. Cross-sectional EBSD mapping measurements were carried out to investigate the effect of LT-buffer layer on improvement of crystal quality and stress relief. The optical property of the obtained freestanding GaN film was also determined by PL measurement.     

Undoped High-Resistance GaN Buffer Layer for AlGaN/GaN High-Electron-Mobility Transistors

Technical Physics Letters - It is shown that intentionally undoped high-resistance GaN buffer layers in AlGaN/GaN heterostructures with high electron mobility for transistors can be formed by...     

Thermoelectric properties and thermoelectric devices of free-standing GaN and epitaxial GaN layer

We studied the thermoelectric properties of free-standing GaN (fr-GaN) and epitaxial GaN layer (epi-GaN), and furthermore, we have fabricated thermoelectric devices using these materials. For fr-GaN, the maximum power factor was 7.7 × 10^− 4 W/m K² at 373 K, and for epi-GaN layer, the maximum power factor was 9.4 × 10^− 4 W/m K² at 373 K. The devices fabricated are (a) fr-GaN and chromel of 4 pairs, and (b) epi-GaN and chromel of 3 pairs. The maximum output power and the open output voltage were (a) 3.35 × 10^− 6 W and 2.76 × 10^− 2 V at ΔT = 153 K, and (b) 1.21 × 10^− 7 W and 1.71 × 10^− 2 V at ΔT = 153 K, respectively.     

High quality GaN film overgrown on GaN nanorods array template by HVPE

The high density vertically aligned GaN nanorods array was fabricated by thermal evaporation of GaN powder with the assistance of HCl gas. The GaN nanorods array was used as template for GaN film growth by hydride vapor phase epitaxy (HVPE). The full width at half maximum values (FWHM) of high-resolution X-ray diffraction (HRXRD) rocking curves for the GaN film with GaN nanorods array template are 247 arc sec (002 reflection) and 308 arc sec (102 reflection), while those for the GaN film without GaN nanorods array template are 292 and 369 arc sec, respectively. This result indicates a significant reduction of dislocation density in the overgrown GaN film with GaN nanorods array template. Photoluminescence spectra measurements reveal the compressive strain relaxation and an improvement in the quality of the overgrown GaN film with GaN nanorods array template as compared to the regrown GaN film without GaN nanorods array template, which is consistent with the trend observed by HRXRD.     

Two-photon spectroscopy in GaN

Two-photon spectroscopy allows to observe unambigously the free A, B, and C excitons with n=2 in bulk GaN. Their energies allow the precise determination of the three band gaps and of the exciton binding energies.     

GaN光导型紫外探测器

研究了以金属有机物化学气相沉积方法生长在６Ｈ－ＳｉＣ衬底上的ＧａＮ光导型紫外探测器的光电流性质。通过光电流谱的测量，获得了ＧａＮ探测器在波长２５０ｎｍ－３６０ｎｍ范围近于平坦的光电流响应，并且观察到在３６５ｎｍ（￣３．４ｅＶ）带边附近陡峭的截止边。测得ＧａＮ探测器在５Ｖ偏压下在３６０ｎｍ波长处的光电流响应度为１３３Ａ／Ｗ，并得到了其响应度与外加偏压的关系。通过拟合光电信号强度与入射光调制频率的实验     

Single crystal GaN nanowires

Single crystal gallium nitride nanowires have been obtained by heating gallium acetylacetonate in the presence of carbon nanotubes or activated carbon in NH3 vapor at 910 degrees C. GaN nanowires also were obtained when the reaction of gallium acetylacetonate with NH3 was carried out over catalytic Fe/Ni particles dispersed over silica. The former procedure with carbon nanotubes is preferable because it avoids the presence of metal particles in the nanowire bundles.     

Bulk large-area GaN layers

Mirror-smooth, transparent bulk GaN layers with an area of 2×3 cm² and a thickness of up to 1 mm were grown by hydrochloride vapor-phase epitaxy. Cracking of the material was eliminated by using a two-stage growth process; separation from a substrate was provided by a low-temperature buffer layer of preset thickness. For the best samples, FWHM of the X-ray rocking curve was ω_θ=3.5′ and the dislocation density amounted to 10⁷–10⁸ cm⁻².