From research to manufacture—The evolution of MOCVD

The article provides an overview of the manufacturing capabilities of metalorganic chemical vapor deposition (MOCVD) technology and describes its application to the growth and fabrication of devices in three different material groups: AlGaAs/GaAs, AlInGaP, and AlGaN/GaN. Discussed are GaN blue light-emitting diodes (LEDs), AlInGaP red and yellow LEDs, and AlGaAs/GaAs vertical cavity surface-emitting lasers and high-electron-mobility transistors. Based on these examples, the evolution of MOCVD technology from fundamental materials studies and advanced materials development through the early stages of pilot manufacturing and large-volume manufacturing capabilities is demonstrated.     

MOCVD Growth of Doped GaAs/AlGaAs Quantum Heterostructures

The influences of growth techniques of AP-MOCVD GaAs/AlGaAs silicon-doped multi-quantum wells(MQWs), heterostructure bipolar transistors (HBTs), double barrier resonant tunneling diodes(DBRTDs) ontheir structures and performances were studied. Continuously grown MQWs, that is, no growth interruption atthe heterointerfaces, shown blue-shifted, narrower and stronger photoluminescence(PL) compared withinterruptedly grown ones.TEM examination of the interrupted interfaces revealed a bright line correspondingto the compositional fluctuation and impurity adsorption, and indicated noncommutative structures ofAlGaAs/GaAs and GaAs/AlGaAs interfaces. High performance HBTs and DBRTDs were obtained bycontinuously grown method while growth interruption caused performance degradation. It was concluded thatgrowth interruption may cause accumulation of residua1 impurities in the ambient as well as compositionalfluctuation while continuous growth at very low growth rates can overcome such problems.     

Atomic-layer epitaxy for heterostructures

Atomic-layer epitaxy offers the ultimate control of interface abruptness and thickness uniformity across a large-area wafer. In the work reported here, GaAs, AlGaAs, and InGaP were grown by atomic-layer epitaxy with one monolayer of growth per deposition cycle. Atomic-layer-epitaxy-grown AlGaAs/ GaAs quantum well structures showed excellent thickness uniformity, and resonant tunneling diodes showed excellent uniformity in both threshold voltage and threshold current. GaInP/GaAs quantum structures were grown and studied; they had well widths as thin as One lattice constant. This 5.6 Å GaAs quantum well is believed to be one of the thinnest grown in this material system.     

Effect of growth interruption and strain buffer layer on PL performance of AlGaAs／GaAs／InGaAs quantum well for 1065 nm wavelength lasers

Strained InGaAs/GaAs quantum well (QW) was grown by low-pressure metallorganic chemical vapor deposition (MOCVD). Growth interruption and strain buffer layer were introduced to improve the photoluminescence (PL) performance of the InGaAs/GaAs quantum well. Good PL results were obtained under condition of growth an interruption of 10 s combined with a moderate strain buffer layer. Wavelength lasers of 1064 nm using the QW were grown and processed into devices. Broad area lasers (100 μm × 500 μm) show very low threshold current densities (43 A/cm2) and high slop efficiency (0.34 W/A, per facet).     

High electron mobility of modulation doped GaAs after growing InP by solid source molecular beam epitaxy

1　INTRODUCTIONModulation doping produced high mobilitytwo dimensional electron gas ( 2DEG) in the Al GaAs/GaAs heterointerface by the physical separa tion of free electrons from positively ionized moth er donors[1, 2]. Modulation doped heterostructurehave attracted much interest for high speed de vices[3 5], low noise microwave amplifiers[6] and formillimeter wave integrated circuits(MMICs)[7] be cause of the extremely high mobility of two dimen sional electron…     

Kinetic study on uniformity of AlGaAs grown by MOVPE

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Preparation and Interface Studies on HgCdTe/CdTe/GaAs Grown by MOCVD

When we use MOCVD technique,an excellent CdTe epi-layer was grown on GaAs substrates and theCdTe/GaAs hybrid substrates suitable for growing Hg_(1-x)Cd_xTe(CMT)were obtained.The x value in CMT isbetween 0.2 and 0.8.The electrical properties of CMT depend upon the thickness of CdTe epi-layers.TheCdTe/GaAs interface was examined by both scanning electron microscope(SEM)and electron auger spectra(EAS).The influence of defects observed at interface on electrical and optical properties of CMT fihns was dis-cussed.     

MOCVD Growth of GaAs / Al_xGa_(1-x) As Superlattices

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Characterizing III–V heteroepitaxial structures

A complementary characterization scheme for high-volume production of III–V heteroepitaxial structures is described, focusing on the cost-effectiveness and utility of the techniques, AlGaAs/InGaAs/GaAs heteroepitaxial layers grown by molecular beam epitaxy were studied by cross-sectional transmission electron microscopy (TEM) and photoluminescence (PL) techniques. The presence of a range of layer thicknesses, fine periodic striation contrast due to Al composition variations, and layer contrasts in the lattice images observed by TEM in selected samples are discussed. The utility of room-temperature PL characterization for AlGaAs/InGaAs/GaAs heteroepitaxial layers is presented. Measures of layer thicknesses and alloy content as well as overall psuedomorphic high-electron-mobility transistor quality and channel sheet charge are derived from the PL signatures.     

The high-volume production of heterojunction bipolar transistors

The insertion of advanced microwave devices into high-volume applications is critically dependent upon a robust and reproducible epitaxial growth technology accompanied with a reproducible process technology. The precise control of the material and device parameters is essential to maintain a high-yield process, which leads to a low-cost product. Although AlGaAs/GaAs heterojunction bipolar transistors have been widely demonstrated in many company research laboratories and universities, the transition from a laboratory environment to high-volume production requires a thorough understanding of the metalorganic chemical vapor deposition growth process and its correlation with device performance. In this work, high-performance AlGaAs/GaAs heterojunction bipolar transistors grown by MOCVD with excellent control in the device parameter tolerances have been demonstrated in very high volumes. N. Pan earned his Ph.D. in electrical engineering at the University of Illinois in 1988. He is currently chief scientist at Kopin Corporation. Dr. Pan is a member of TMS. D. Hill earned his M.S. in materials science at the Polytechnic Institute of New York in 1986. He is currently vice president of epioperations at Kopin Corporation. Mr. Hill is also member of TMS. C. Rose earned his M.S. in advanced manufacturing engineering at Worcester Polytechnic Institute in 1990. He is currently a quality assurance engineer at Kopin Corporation. R. McCullough earned his A.S. in mechanical design engineering at Wentworth Institute of Technology in 1970. He is currently engineering manager at Kopin Corporation. P. Rice earned his BSEET in electrical engineering at Wentworth Institute of Technology in 1990. He is currently a characterization engineer at Kopin Corporation. D.P. Vu earned his Ph.D. in solid-state physics at Louis Pasteur Institute in 1983. He is currently a principal scientist at Kopin Corporation. K. Hong earned his Ph.D. in electrical engineering at the University of Michigan in 1996. He is currently an electronic design engineer at Rockwell Semiconductor Systems. C. Farley earned his Ph.D. in engineering at the University of Texas at Austin in 1986. He is currently manager, advanced device technology, at Rockwell Semiconductor Systems.     

Characterization of GaSb Films by Metalorganic Chemical Vapour Deposition

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红外光电薄膜材料的界面结构与光电性能

分析了InAs/GaInSb应变层超晶格、AlGaN/GaN量子阱和超晶格红外光电薄膜材料的界面结合类型及其对材料界面结构和光电性能的影响.描述了在超晶格界面处的原子置换和扩散现象.阐述了分子束外延生长过程中控制量子阱超晶格界面结构的工艺方法.试验结果表明,调节组元的束流和采用表面迁移增强外延技术可以有效控制界面处的原子交换过程,从而提高薄膜材料的生长质量.     

Preliminary Study on Electrical and Optical Properties of ZnO Film Grown by MOCVD

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Investigation of EL2 Defect in 10 MeV Electron Irradiated Undoped Semi－insulating LEC GaAs

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Influence of pulse parameters on the microstructure and microhardness of nickel electrodeposits

Square-wave cathodic current modulation was used to electrodeposit fine-grained nickel from an additive-free and saccharin-containing Watts bath. The influence of pulse on-time, off-time, peak current density and saccharin on the grain size, surface morphology, crystal orientation, and microhardness was determined. The study showed that at constant off-time and peak current density, the crystal size of the deposits was found initially to decrease with pulse on-time before it started to increase with further increase in on-time. The crystal orientation progressively changed from a (111) texture at the on-time of 0.1 ms to a strong (200) texture at an on-time of 8 ms. An increase in the pulse off-time at constant on-time and peak current density resulted in a progressive increase in crystal size. However, the crystal orientation remained unaffected with increasing off-time. An increase in peak current density resulted in considerable refinement in crystal size of the deposits. The crystal orientation progressively changed from an almost random distribution at the lowest peak current density of 0.2 A/m² to a strong (200) texture at a peak current density of 2.0 A/m². The nanocrystalline nickel with grain size in the order of 30 nm can be produced from saccharin-containing Watts' baths. In contrast, when using an organic-free Watts' bath and similar pulse-plating conditions, the grain size can only be refined down to about 80-100 nm. The microhardness of deposits is related with grain size: when the grain size is large, the microhardness is consistent with Hall-Petch law (HPL); when the grain size is ultrafine, “nano-effect” would be generated, the microhardness is against HPL.     

电场强度对Ti纳米晶薄膜生长模式及性能的影响

采用强脉冲电场条件下物理气相沉积的方法,通过大幅提高脉冲峰值电流的方式,获得晶粒尺寸细小的Ti纳米晶薄膜,并依次对薄膜的生长模式及相关性能进行了对比研究。结果表明:较大的峰值电流可以获得晶粒尺寸细小的Ti纳米晶薄膜,但峰值电流的增大不能改变薄膜内晶体以Ti(100)晶面择优生长。薄膜的表面生长形貌表现为随峰值电流的增大,颗粒间隙大幅降低、粒子团聚尺寸增大、整体呈现圆球状紧密生长的结构。截面生长形貌表现为随峰值电流的增大逐渐由纤维状向柱状形貌过渡,并有效降低薄膜的内部缺陷,致密度显著提高。力学性能表现为随峰值电流的增大,薄膜的硬度、模量都呈现出先增大后减小的变化趋势,且当峰值电流增大到30~45 A之间时,Ti薄膜的硬度与模量存在最大值。     

1-丁基-3-甲基咪唑四氟硼酸盐离子液体电沉积制备Ir研究

本文研究了在离子液体1-丁基-3-甲基咪唑四氟硼酸盐中电沉积制备Ir的电化学行为,在金电极上获得的循环伏安特性曲线表示,Ir(III)经过一步还原反应生成Ir,并且该反应是由Ir(III)离子的扩散控制的不可逆过程。其中,扩散速率为3.83×10_?11 m₂/s,平均传质系数为0.083。本文用扫描电镜(SEM)、X-射线衍射(XRD)及X-射线光电子能谱(XPS)研究了在钼基体上获得的Ir层的表面形貌及组成,结果显示,Ir层的形貌与沉积电位、时间及电流密度有关。恒电位电沉积过程中,在还原峰电位处由于成核及生长速率达到平衡,可以获得相对致密的镀层。在恒电流电沉积中,当电流密度在0.5~1.82 mA/cm₂时可以得到平整致密的Ir镀层。     

Growth of high-quality thick GaN using a tungsten interlayer

A high-quality GaN film was (W-GaN) grown by hydride vapor phase epitaxy (HVPE) on metalorganic chemical vapor deposition (MOCVD) GaN templates with a tungsten (W) interlayer.A sample without interlayer was also grown at the same time for comparison.Significant reductions of dislocation density in W-GaN film is confirmed by the result of high-resolution X-ray diffraction and transmission electron microscope (TEM) observation.The improvement of optical properties of the W-GaN is confirmed by photoluminescence (PL) result.A shift of PL peak suggests that the strain is lower in the W-GaN than the film without W interlayer.This technique offers a potential path to obtain high-quality GaN film as free-standing substrate.     

Hot Tensile Behaviors and Microstructure Evolution of Ti-6Al-4V Titanium Alloy Under Electropulsing

The effect of electropulsing on the mechanical behaviors and microstructures of Ti-6Al-4V titanium alloy was investigated by an uniaxial tensile test. Compared to the value measured in cold tensile test, the alloy exhibits lower ultimate tensile strength when the tensile deformation is assisted by electropulsing. The tensile elongation is found to vary non-monotonically with increasing root mean square(RMS) current density. Though decreasing at first, the tensile elongation increases with current density once the value exceeds 8.1 A/mm~2. Through applying current with RMS current density of 12.7 A/mm~2, the tensile elongation at strain rate 0.001 s~(-1) can be improved by 94.1%. In addition, it is observed that more remarkable electroplastic effect is induced by the higher peak current density under similar thermal effect. Microstructure analysis reveals that the low plasticity at 8.1 A/mm~2 is attributed to the micro-void easily formation near the tips of acicular β phases. The enhanced ductility at higher current densities, on the other hand, is attributed to the dynamic recrystallization.