Influence of double AlN buffer layers on the qualities of GaN films prepared by metal-organic chemical vapour deposition

In this paper we report that the GaN thin film is grown by metal-organic chemical vapour deposition on a sapphire （0001） substrate with double A1N buffer layers. The buffer layer consists of a low-temperature （LT） A1N layer and a high-temperature （HT） A1N layer that are grown at 600 ℃ and 1000 ℃, respectively. It is observed that the thickness of the LT-A1N layer drastically influences the quality of GaN thin film, and that the optimized 4.25-min-LT-A1N layer minimizes the dislocation density of GaN thin film. The reason for the improved properties is discussed in this paper.

Photoluminescence and lasing properties of InAs/GaAs quantum dots grown by metal-organic chemical vapour deposition

Photoluminescence （PL） and lasing properties of InAs/GaAs quantum dots （QDs） with different growth procedures prepared by metalorganic chemical vapour deposition are studied. PL measurements show that the low growth rate QD sample has a larger PL intensity and a narrower PL line width than the high growth rate sample. During rapid thermal annealing, however, the low growth rate sample shows a greater blueshift of PL peak wavelength. This is caused by the larger InAs layer thickness which results from the larger 2-3 dimensional transition critical layer thickness for the QDs in the low-growth-rate sample. A growth technique including growth interruption and in-situ annealing, named indium flush method, is used during the growth of GaAs cap layer, which can flatten the GaAs surface effectively. Though the method results in a blueshift of PL peak wavelength and a broadening of PL line width, it is essential for the fabrication of room temperature working QD lasers.

Fabrication of 160-nm T-gate metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by metal organic chemical vapour deposition

The fabrication and performance of 160-nm gate-length metamorphic AlInAs/GaInAs high electron mobility transistors （mHEMTs） grown on GaAs substrate by metal organic chemical vapour deposition （MOCVD） are reported. By using a novel combined optical and e-beam photolithography technology, submicron mHEMTs devices have been achieved. The devices exhibit good DC and RF performance. The maximum current density was 817 mA/mm and the maximum transconductance was 828 mS/mm. The non-alloyed Ohmic contact resistance Rc was as low as 0.02 Ω- ram. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） were 146 GHz and 189 GHz, respectively. This device has the highest fT yet reported for a 160-nm gate-length HEMTs grown by MOCVD. The output conductance is 28.9 mS/mm, which results in a large voltage gain of 28.6, Also, an input capacitance to gate-drain feedback capacitance ratio, Cgs/Cgd, of 4.3 is obtained in the device.

Growth and characterization of InAsSb alloys by metalorganic chemical vapour deposition

Low pressure metalorganic chemical vapour deposition （LP-MOCVD） growth and characteristics of InAsSb on （100） GaSb substrates are investigated. Mirror-like surfaces with a minimum lattice mismatch are obtained. The samples are studied by photoluminescence spectra, and the output is 3.17μm in wavelength. The surface of InAsSb epilayer shows that its morphological feature is dependent on buffer layer. With an InAs buffer layer used, the best surface is obtained. The InAsSb film shows to be of n-type conduction with an electron concentration of 8.52 × 10^16 cm^-3.

Metal Organic Chemical Vapour Deposited Thin Films of Cobalt Oxide Prepared via Cobalt Acetylacetonate

The single solid source precursor, cobalt （Ⅱ） acetylacetonate was prepared and characterized by infrared spectroscopy. Thin films of cobalt oxide were deposited on soda lime glass substrates through the pyrolysis （metal organic chemical vapour deposition （MOCVD）） of single solid source precursor, cobalt acetylacetonate, Co[C5H7O2]2 at a temperature of 420℃. The compositional characterization carried out by rutherford backscattering spectroscopy and X-ray diffraction （XRD）, showed that the films have a stoichiometry of Co2O3 and an average thickness of 227±0.2 nm. A direct energy gap of 2,15±0.01 eV was calculated by the data obtained by optical absorption spectroscopy. The morphology of the films obtained by scanning electron microscopy, showed that the grains were continuous and uniformly distributed at various magnifications, while the average grain size was less than i micron for the deposited thin films of cobalt oxide.

Synthesis and Characterization of Metal Organic Chemical Vapour Deposited Copper Titanium Oxide (Cu-Ti-O) Thin Films from Single Solid Source Precursor

Thin films of copper titanium oxide were deposited by metal organic chemical vapour deposition technique from the synthesized single solid source precursor, copper titanium acetylacatonate Cu [Ti(C5H7O2)3] at the deposition temperature of 420°C. The deposited films were characterized using Rutherford Backscattering Spectroscopy, Scanning Electron Microscopy with Energy Dispersive X-Ray facility attached to it, X-Ray Diffractometry, UV-Visible Spectrometry and van-der Pauw Conductivity measurement. Results show that the thickness of the prepared film is determined as 101.236 nm and the film is amorphous in structure, having average grain size of approximately 1 μm. The optical behaviour showed that the absorption edge of the film was at 918 nm near infrared with corresponding direct energy band gap of 1.35 eV. The electrical characterization of the film gave the values of resistivity, sheet resistance and conductivity of the film as 3.43 × 10-1 Ω-cm, 3.39 × 106 Ω/square and 2.91 (Ω-cm)-1 respectively.

Zn/O ratio and oxygen chemical state ofnanocrystalline ZnO films grown atdifferent temperatures

ZnO nanocrystalline films are prepared on Si substrates at different temperatures by using metal-organic chemical vapour deposition （MOCVD）. It is observed that when the growth temperature is low, the stoichiometric ratio between Zn and 0 atoms has a large deviation from the ideal ratio of 1：1. The ZnO grains in the film have small sizes and are not well crystallized, resulting in a poor photoluminescence （PL） property. When the temperature is increased to an appropriate value, the Zn/O ratio becomes optimized, and most of Zn and 0 atoms are combined into Zn-O bonds. Then the film has good crystal quality and good PL property. If the temperature is fairly high, the interracial mutual diffusion of atoms between the substrate and the epitaxial film appears, and the desorption process of the oxygen atoms is enhanced. However, it has no effect on the film property. The film still has the best crystal quality and PL property.

MOCVD法制备金属陶瓷功能梯度材料的研究

利用金属有机化学气相沉积(MOCVD)方法,以Mo(CO)6,Si(OC2H5)4为物源,在Al2O3陶瓷基片上制备了金属陶瓷功能梯度材料,并用XPS,XRD,SEM等技术对其成分分布,物相组成和表面形貌进行测试和表征.结果表明:材料的组成沿厚度方向呈连续梯度变化,符合功能梯度材料的变化规律.

MOCVD掺A_s的S_nO_2透明导电膜

本文采用有机金属化合物气相沉积（MOCVD）技术制备了可见光透过率】90％（厚度为102-104）、薄层方块电阻值为38-56Ω/□的SO2·A,多晶透明导电薄膜,并简要报道了利用X射线衍射、电子衍射、扫描电子显微镜以及紫外可见吸收光谱等方法对膜层结构及性能的研究结果。

气相色谱分析MOCVD中的Ⅲ-Ⅴ族挥发性无机氢化物及其反应尾气

为配合Ⅲ Ⅴ族半导体研制和评定金属有机物化学气相沉积 (简称MOCVD)装置的尾气处理效果 ,及其对安全的影响 ,研究了用气相色谱对所用的高纯氢化物的杂质、检测灵敏度及相对保留值 ;混合氢化物的组分 ;反应尾气中有害物在处理前后的含量变化等进行了测定。组分分离较好 ,相对标准误差小于 2 3 %。

High-responsivity solar-blind photodetector based on MOCVD-grown Si-dopedβ-Ga_(2)O_(3)thin film

Si-dopedβ-Ga_(2)O_(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 mA under 200μW·cm^(-2)254 nm illumination and±20 V bias,leading to photo-responsivity as high as 788 A·W^(-1).The Si-dopedβ-Ga2O3-based PD is promised to perform solar-blind photodetection with high performance.

Synthesis and Some Properties of Metal Organic Chemical Vapour Deposited Molybdenum Oxysulphide Thin Films

Molybdenum oxodithiocarbamate was prepared as thin films which were deposited on sodalime glass a single solid source precursor for molybdenum oxysulphide substrates using metal organic chemical vapour deposition （MOCVD） technique at a temperature of 420~C. Rutherford backscattering spectroscopy （RBS） was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy （SEM） micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 #m. X-ray diffraction （XRD） showed that the deposited films were crystalline in nature.

InGaAs/GaAsP应变补偿多量子阱MOCVD生长

利用金属有机化学气相沉积技术在GaAs衬底上开展了大失配InGaAs多量子阱的外延生长研究。针对InGaAs与GaAs之间较大晶格失配的问题,设计了GaAsP应变补偿层结构;通过理论模拟与实验相结合的方式,调控了GaAsP材料体系中的P组分,设计了P组分分别为0,0.128,0.184,0.257的三周期In_(x)Ga_(1-x)As/GaAs_(1-y)P_(y)多量子阱结构;通过PL、XRD、AFM测试对比发现,高势垒GaAsP材料的张应变补偿可以改善晶体质量。综合比较,在P组分为0.184时,PL波长1043.6 nm,半峰宽29.9 nm,XRD有多级卫星峰且半峰宽较小,AFM粗糙度为0.130 nm,表面形貌显示为台阶流生长模式。

Hetero-epitaxy of L_g= 0.13-μm metamorphic AlInAs/GaInAs HEMT on Si substrates by MOCVD for logic applications

In this work, a hetero-epitaxial Al0.49In0.51As/Ga0.47In0.53 As metamorphic high electron mobility transistor(mHEMT) grown by metal–organic chemical vapor deposition(MOCVD) on p-type silicon substrate has been successfully demonstrated. A novel AlGaAs/Al As period multiple quantum well(MQW) composite buffer scheme is developed to effectively tune the leakage current from the buffer layer. The quantized room-temperature Hall mobility of the twodimensional electron gas(2DEG) is larger than 7800 cm2/V·s, with an average sheet carrier density of 4.6×1012cm-2.Two-stage electron beam(EB) lithography technology by a JBX-6300 e-beam lithography system is developed to realize a 0.13-μm m HEMT device on Si substrate. A maximum transconductance Gm of up to 854 mS/mm is achieved, and is comparable to that of m HEMT technology on Ga As substrate with the same dimension. The fTand fmax are 135 GHz and120 GHz, respectively.

MOCVD of Molybdenum Sulphide Thin Film Via Single Solid Source Precursor Bis-(Morpholinodithioato-s,s’)-Mo

A single solid source precursor bis-(morpholinodithioato-s,s’)-Mo was prepared and molybdenum sulphide thin film was deposited on sodalime glass using Metal Organic Chemical Vapour Deposition (MOCVD) technique at deposition temperature of 420?C. The film was characterized using Rutherford Backscattering Spectroscopy (RBS), Ultraviolet-Visible Spectroscopy, Four point probe technique, Scanning Electron Mi-croscopy (SEM), X-ray Diffractometry (XRD) and Atomic Force Microscopy (AFM). A direct optical band gap of 1.77 eV was obtained from the analysis of the absorption spectrum. The sheet resistance was found to be of the order of 10P–5P ΩP–1P?cmP–1P. SEM micrographs of the films showed the layered structure of the film with an estimated grain size that is less than 2 μm while XRD indicates parallel orientation of the basal plane to the substrate surface.

Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.

Characterization of the N-polar GaN film grown on C-plane sapphire and misoriented C-plane sapphire substrates by MOCVD

Gallium nitride(GaN) thin film of the nitrogen polarity(N-polar) was grown on C-plane sapphire and misoriented C-plane sapphire substrates respectively by metal-organic chemical vapor deposition(MOCVD). The misorientation angle is off-axis from C-plane toward M-plane of the substrates, and the angle is 2°and 4°respectively. The nitrogen polarity was confirmed by examining the images of the scanning electron microscope before and after the wet etching in potassium hydroxide(KOH) solution. The morphology was studied by the optical microscope and atomic force microscope. The crystalline quality was characterized by the x-ray diffraction. The lateral coherence length, the tilt angle, the vertical coherence length, and the vertical lattice-strain were acquired using the pseudo-Voigt function to fit the x-ray diffraction curves and then calculating with four empirical formulae. The lateral coherence length increases with the misorientation angle, because higher step density and shorter distance between adjacent steps can lead to larger lateral coherence length.The tilt angle increases with the misorientation angle, which means that the misoriented substrate can degrade the identity of crystal orientation of the N-polar GaN film. The vertical lattice-strain decreases with the misorientation angle. The vertical coherence length does not change a lot as the misorientation angle increases and this value of all samples is close to the nominal thickness of the N-polar GaN layer. This study helps to understand the influence of the misorientation angle of misoriented C-plane sapphire on the morphology, the crystalline quality, and the microstructure of N-polar GaN films.

Effects of Growth Conditions on the Microstructure Characteristics of CdS Thin Films by AP-MOCVD

Growth of cadmium sulfide （CdS） thin films on glass substrates was carried out by atmospheric pressure metal-organic chemical vapor deposition （AP-MOCVD） using Cd（S2CNEt2）2 as the single precursor. Changes in the surface morphology of the deposited CdS thin films were investigated by atomic force microscope （AFM） as the function of substrate temperature （Ts）, vaporizing temperature （Tv）, and Ar flow rate. With the increase of Tv, CdS thin films evolved from pyramidal structure with fine grains to columnar structure with large grains. X-ray diffraction （XRD） patterns indicated that the CdS films had random orientation at the lower Tv and preferred orientation at the higher Tv. In addition, Ts had a great effect on the surface roughness of the CdS films, and a quantum dot-like structural CdS films were obtained in a narrow range of Ts with high Ar flow rate. Furthermore, the optical properties of the CdS films were measured using ultraviolet-visible （UV/VIS） spectrometer.

用于日盲波段的MgZnO薄膜材料和紫外探测器

考虑ZnO优秀的物理和化学性能以及由于生长温度低而具有更低的缺陷密度从而易于实现高的光电器件效率等特点,本文采用射频磁控溅射和金属有机化学汽相沉积(MOCVD)方法在石英及蓝宝石衬底上生长了立方结构MgZnO薄膜,制备了MgZnO的MSM型紫外探测器。该器件实现了在日盲(太阳盲)波段的光响应,典型的光响应峰值分别在225和250 nm,截止边为230和273 nm。