Characterization of AlxGa1−xAs/GaAs heterostructures for single quantum wells grown by a solid arsenic MOCVD system

This work presents the results of the growth and characterization of Al_xGa_1−xAs/GaAs multilayer structures obtained in a metallic-arsenic-based-MOCVD system. The main goal is to explore the ability of the growth system to grow high quality multilayer structures like quantum wells. The use of metallic arsenic could introduce important differences in the growth process due to the absence of the hydride group V precursor (AsH₃), which manifests in the electrical and optical characteristics of both GaAs and Al_xGa_1−xAs layers. The characterization of these epilayers and structures was performed using low-temperature photoluminescence, Hall effect measurements, X-ray diffraction, Raman spectroscopy, secondary ion mass spectroscopy (SIMS) and Atomic Force Microscopy (AFM).     

The luminescence of ZnO film grown on GaAs interlayer by PA-MOCVD

ZnO film was firstly prepared by PA-MOCVD method on the substrate pre-coated with GaAs interlayer. Hall measurement found that the GaAs interlayer had important effects on the electrical behavior of the ZnO film. It could make the ZnO film convert to p-type conductivity. The XPS results confirmed that the acceptor was arsenic. And the acceptor level was 130 meV above the ZnO valence band maximum. Low-temperature PL measurement was introduced to investigate the optical properties of both as-grown n-type and arsenic doped p-type ZnO films. Then, based on this technology, ZnO homojunction light emitting device (LED) was fabricated with arsenic doped p-type ZnO and unintentionally doped n-type ZnO on GaAs/p⁺-Si substrate. Its current-voltage (I-V) character showed a typical rectification behavior, which was different from the n-ZnO/p⁺-Si structure. The UV-visible (385-580 nm) electroluminescence was detected under relatively low current injection condition from the n-ZnO/p-ZnO/p⁺-Si LED.     

低压-MOCVD方法制备CdS-ZnS应变多量子阱

本文报道了用低压(LP)-MOCVD方法制备CdS-ZnS应变多量子阱结构.通过X-射线衍射谱证实了所制备的样品具有比较好的多层结构,并通过77K下的光致发光(PL)光谱,观测到了大的垒层对电子的限制效应及由大的应变引起的阱层带边变化所导致的发光峰蓝移.     

常压MOCVD法生长的p型ZnSe及其光电特性

本文通过常压MOCVD方法,利用NH₃气作为受主掺杂源,在(100)方向的GaAs衬底上生长了ZnSe:N膜。通过测量77K温度下光致发光光谱。观测到了由于掺氮引起的自由到束缚发射(FA)和深中心复合(SA).在低掺杂浓度下FA起主要作用,随着NH₃气浓度增加,FA和SA带的强度随之增强,在重掺杂下SA带成为主要,同时带的半宽度展宽。室温下霍尔测量的结果表明。低掺杂浓度下ZnSe:N膜呈高阻态,而在高掺杂浓度下外延膜呈现P型电导,载流子浓度P～1016cm³.利用p-ZnSe/n-GaAs构成异质pn结,观测到了二极管的整流特性,进一步证实p型ZnSe的实现。     

实用化微机全自动控制XG60-1型MOCVD装置的研制

本文介绍的是自行设计与制造的高度自动化MOCVD装置。该装置设有9路流量控制管路,6路源,1路HCl气源及氯气旁路,装置气密性好,8 kg/cm²正压时,用Snoop溶液检测无泄露。配有真空机组,反应室可抽至10^-5乇。反应室为高频加热,控温精度±0.2℃,有机源冷井控温精度±0.1℃,设有压力,H₂、AsH₃、PH₃报警及自动处置系统,有断水,断电保护,全部控制量均为数字显示,温度及全部流量的设置与调整均实现微机自动控制,配有GaAs,AlGaAs单层及多层结构生长工艺的专用软件,实现完全自动化生长。该装置性能稳定,重复性好,安全可靠,对操作者及环境无危害,设有手动及自动转换开关,适合于科研和生产使用。     

XPS study of impurities in Si‐doped AlN film

This paper reports an XPS study of impurities in a 100‐nm‐thick AlN film grown by metalorganic chemical vapor deposition (MOCVD) under low pressure on the n‐type 6H‐SiC substrate. The Si‐doped AlN film was characterized by the X‐ray photoelectron spectroscopy (XPS) in a high vacuum system, which reveals the content distribution and chemical states of impurities along depth. The XPS analysis of AlN film before and after argon‐ion etching indicates that there always exist Ga, O and C contaminations in AlN film. Especially, O contamination on the AlN film surface is mostly introduced during the growth of AlN layer by MOCVD. Meanwhile, most of O atoms bind with Al or Ga in Al―O and Ga―O chemical states. In particular, the Ga atoms in AlN film are always in two chemical states, i.e. Ga―Ga bond and Ga―O bond, which demonstrates that the aggregation of Ga is accompanying with AlN growth. Copyright © 2016 John Wiley & Sons, Ltd.     

High-responsivity solar-blind photodetector based on MOCVD-grown Si-doped β-Ga_2O_3 thin film

Si-doped β-Ga_2O_3 films are fabricated through metal-organic chemical vapor deposition(MOCVD). Solar-blind ultraviolet(UV) photodetector(PD) based on the films is fabricated by standard photolithography, and the photodetection properties are investigated. The results show that the photocurrent increases to 11.2 m A under 200 μW·cm-2254 nm illumination and ±20 V bias, leading to photo-responsivity as high as 788 A·W~(-1). The Si-doped β-Ga_2O_3-based PD is promised to perform solar-blind photodetection with high performance.     

Cu/MgO催化剂的MOCVD法制备及其γ-戊内酯加氢制1,4-戊二醇性能

以Cu（acac）₂为金属有机铜前体,层状MgO为载体,采用金属有机化学气相沉积方法（MOCVD）制备了Cu/MgO催化剂,并通过X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、场发射扫描电镜（FE-SEM）、透射电子显微镜（TEM）和N₂物理吸附等方法对Cu/MgO催化剂结构进行表征。结果表明,有机铜前体沉积在了MgO上,并且在沉积后,载体MgO的晶体结构仍然保留完整。利用生物质平台分子γ-戊内酯加氢反应来评价Cu/MgO催化剂的催化性能。研究表明,在473 K和10 MPa反应条件下,18% Cu/MgO催化剂表现出优异的催化活性（90.5%）和1,4-戊二醇选择性（94.4%）,且催化剂循环三次,催化活性没有显著降低。     

Optical and crystal improvements of semipolar (11-22) GaN/m-sapphire by in-situ thermal etching process

We investigated the optical and crystal qualities of semipolar (11-22) GaN grown on m-plane sapphire using three-step growth technique which consisted of seed GaN growth, in-situ thermal etching process (I-STEP), and lateral growth step. By introducing three-step growth, we achieved high optical and crystal qualities of semipolar (11-22) GaN films compared with those grown by conventional one-step growth. In particular, as the positions of I-STEP were decreased from 1.0 to 0.25 μm toward sapphire substrate, the full width at half maximum of the X-ray rocking curve was effectively decreased from 1083 to 828 arcsec, respectively. Furthermore, photoluminescence results showed that the bandedge emission intensity of semipolar (11-22) GaN with I-STEP was 56% higher than that with conventional growth technique. Based on these results, we suggested that the three-step growth would be effective to improve the crystal and optical qualities of semipolar (11-22) GaN/m-sapphire.