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.     

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…     

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).     

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.     

Modified AlAs/GaAs Double Barrier Quantum Resonant Tunneling Diodes Grown by AP-MOCVD

The MOCVD growth of modified AlAs/GaAs double barrier resonant tunneling diodes(DBRTD)withan A1GaAs chair was reported.The resonances to the first excited states were obtained.The peak-to-valley cur-rent ratio(PVCR)is 1.3 at 77K,room temperature peak current density is 8 kA/cm~2.The resonance voltagesare in agreement with the theoretical approach by transfer-matrix method.Influence of interrupted growthtime at the hetero-interface and incorporation of the AlGaAs chair to the device performances were studiedand the mechanism was discussed.The attempt to add an AlGaAs chair to the DBRTD by MOCVD resultedin improvement in the PVCR and peak current density.     

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.     

Kinetic study on uniformity of AlGaAs grown by MOVPE

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Low temperature OMVPE growth of ZnSe withTertiary-butyl allyl selenide and dimethylzinc-triethylamine

The growth of high quality ZnSe by organometallic vapor phase epitaxy (OMVPE) has been investigated fortertiary-butyl allyl selenide (tBASe), combined with dimethylzinc-triethylamine (DMZn : NEt₃). Single crystalline ZnSe films were grown on GaAs at temperature as low as 350°C with a reasonable growth rate (~1 µm/h). Secondary ion mass spectrometry (SIMS) spectra show a negligible carbon incorporation in ZnSe films from tBASe even at high VI/II ratio, in contrast the carbon concentration of 10²¹ cm^-3 in ZnSe films grown from diallyl selenide (DASe)and methylallylselenide (MASe). Good surface morphology, crystalline and interface quality of ZnSe on (001) GaAs are confirmed by scanning electron microscopy, double crystal diffractometry (DCD) and Rutherford backscattering spectrometry (RBS). Photoluminescence at 10K shows sharp near-band-edge excitonic spectra.     

InGaP/InGaAs/GaAs DHBT structural materials grown by GSMBE

Heterojunction bipolar transistor (HBT) is of great interest for the application to microwave power and analog circuits.As known, decreasing bandgap energy of the base layer in HBT can result in a smaller turn-on voltage.Using InGaAs as a base material in GaAs HBT is a possible approach to achieve the aim.In this work, a novel InGaP/InGaAs/GaAs double heterojunction bipolar transistor (DHBT) structure with an InGaAs base was designed and grown by gas source molecular beam epitaxy (GSMBE).High-quality InGaAs/GaAs hetero epi-layers and a good doping figure were obtained through optimizing the layer structure and the growth condition.The DHBT devices of a 120 μm×120 μm emitter area were fabricated by normal process and the good DC performance was obtained.A breakdown voltage of 10 V and an offset voltage of just 0.4 V were achieved.These results indicate that the InGaP/InGaAs/GaAs DHBT is suitable for low power-dissipation and high power applications.     

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.     

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.     

Pd/Ge(or Si)/Pd/Ti/Au ohmic contacts to n-type InGaAs for AlGaAs/GaAs HBTs

Pd/Ge/Pd/Ti/Au and Pd/Si/Pd/Ti/Au ohmic contacts to n-type InGaAs were investigated for applications to AlGaAs/GaAs HBT emitter ohmic contacts. In the Pd/Ge/Pd/Ti/Au ohmic contact, a minimum specific contact resistivity of 1.1×10⁻⁶ Ωcm² was achieved by annealing at 425°C/10s, but the ohmic performance was slightly degraded with increasing annealing temperature due to the reaction between the ohmic contact materials and the InGaAs substrate. However, a non-spiking planar interface and relatively good ohmic contact (high-10⁻⁶ Ωcm²) were maintained after annealing at 450°C/10s. In the Pd/Si/Pd/Ti/Au ohmic contact, in spite of the lower barrier height of the metal-InGaAs junction, as-deposited contacts showed non-ohmic behaviors due to the presence of the insulating Si layer. However, the specific contact resistivity decreased remarkably to 4.3×10⁻⁷ Ωcm² by annealing at 425°C/10s. Minimum specific contact resistivity of 3.9×10⁻⁷ Ωcm² was achieved by annealing at 400°C/20s. RF performance of the AlGaAs/GaAs HBT was also examined by employing the Pd/Ge/Pd/Ti/Au and Pd/Si/Pd/Ti/Au systems as emitter ohmic contacts. Cutoff frequencies were 65.0 GHz and 74.4 GHz, respectively, and maximum oscillation frequencies were 51.3 GHz and 52.5 GHz, respectively, indicating very successful high frequency operations.     

定向凝固包晶合金带状组织的形成机制及相选择Ⅰ.带状组织的形成机制

对定向凝固包晶合金在不同生长条件下,初生相和包晶相分别作为单相和充分形核相以低速平界面生长时,从初始到稳态的整个过渡区间,两相在界面及界面前沿液相中的溶质分布进行了分析,利用充分形核假设和成分过冷准则以及相稳定生长的最高界面温度判据,分析了初始过渡区内可能发生的第二相形核转变,确定了形成带状组织的成分条件,考虑到相生长的历史相关性,将带状组织区分为周期性带状组织区和单一带状组织区,更能够对实验现象进行合理的解释,对Ti-Al合金的计算结果与理论分析一致。     

Interface growth morphologies in pulsed laser deposited, room temperature grown multilayer hard coatings

The mechanical behaviour - hardness, elasticity, and adhesion - of multilayer coatings is strongly influenced by the type of the formed interfaces between the different layers. In industrially applied tribological coatings the interface region is predominantly not a perfect sudden change of the chemical composition of the adjacent crystal planes, but a transition zone of a thickness, which is strongly dependent on the energetic conditions during deposition. Multilayer coatings grown by high-energetic deposition techniques always struggle with high atomic mixing of both adjacent coating materials due to high energetic ion implantation.One of these high-energetic deposition techniques is the Pulsed Laser Deposition (PLD), characterized by pulsed and within one pulse alternating high- and low-energetic particle fractions, hitting successively the substrate surface. Such deposition conditions were shown to be highly advantageous for low temperature deposition by the densification of the growth structures due to activated diffusion and re-sputtering, but increases the difficulty in depositing multilayer structures.The current paper addresses these specific growth conditions based on Ti/TiN and Cr/CrN multilayer coatings. High resolution transmission electron microscopy results show that the atomic mixing at the interface is not highly critical for the deposition of multilayer coatings and that extremely dense growth structures are forming even in the interface regions.     

Three-dimensional atom probe studies of metallic multilayers

Multilayer film structures which exhibit giant magnetoresistance have applications in the areas of magnetic recording and computer memory. The magnetic properties of these structures are highly dependent upon atomic level structural and compositional variations. Thus, structural characterization with extremely high spatial resolution, especially at the interfaces, is very important in order to optimize the performance of these devices with respect to processing and operating conditions. Field-ion microscopy and three-dimensional atom probe microanalysis have been used to characterize the interfaces and grain boundaries in a structure containing 100 repetitions of a (Cu_2 nm/Co_2 nm) bilayer. Analyses show layer alloying, a high degree of layer curvature (particularly close to grain boundaries) and regions where cobalt layers are in contact. In addition, atomic scale analysis of the interface between copper and cobalt layers indicates that atomic planes are coherent from one layer to the next.     

An experimental study about the influence of well thickness on the electroluminescence of InGaN/GaN multiple quantum wells

The influence of well thickness on the electroluminescence (EL) of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition is investigated. It is found that the peak wavelength of EL increases with the increase of well thickness when the latter is located in the range of 3.0–5.1 nm. The redshift is mainly attributed to the quantum confined Stark effect (QCSE). As a contrast, it is found that the EL intensity of InGaN/GaN MQWs increases with the increase of well thickness in spite of QCSE. The result of X-ray diffraction demonstrates that the interface become smoother with the increase of well thickness and suggests that the reduced interface roughness can be an important factor leading to the increase of EL intensity of InGaN/GaN MQWs.     

Thermodynamic study of phase equilibria in strained III–V alloy semiconductors

Phase equilibria in GaSb-GaAs and InAs-GaAs thin films grown on GaAs and InP substrates were calculated, taking into consideration the elastic contribution caused by the lattice mismatch between the film and substrate. The basic concept used in describing the elastic free energy is that strain due to a lattice mismatch accumulates in a thin film and interfacial misfit dislocations form when the strain energy exceeds a certain energy barrier. Our calculations showed that the single-phase region of a zinc-blend-type compound forms in the GaSb-GaAs/InP and InAs-GaAs/InP systems. This result is in fairly good agreement with the experimental examination of epitaxially grown thin film. The compositional latching phenomenon frequently observed in alloy semiconductor systems can be interpreted in terms of the phase separation generated by the accumulated strain in the thin films.     

Thermodynamic study of phase equilibria in strained III–V alloy semiconductors

Phase equilibria in GaSb-GaAs and InAs-GaAs thin films grown on GaAs and InP substrates were calculated, taking into consideration the elastic contribution caused by the lattice mismatch between the film and substrate. The basic concept used in describing the elastic free energy is that strain due to a lattice mismatch accumulates in a thin film and interfacial misfit dislocations form when the strain energy exceeds a certain energy barrier. Our calculations showed that the single-phase region of a zinc-blend-type compound forms in the GaSb-GaAs/InP and InAs-GaAs/InP systems. This result is in fairly good agreement with the experimental examination of epitaxially grown thin film. The compositional latching phenomenon frequently observed in alloy semiconductor systems can be interpreted in terms of the phase separation generated by the accumulated strain in the thin films.     

砷化镓衬底加工技术研究及其新发展

第二代半导体砷化镓(GaAs)材料是衬底外延生长和器件制备的基础材料,其晶片表面要求超光滑、无表面/亚表面损伤和低的残余应力等,且其表面平坦化质量决定了后续外延层的质量,并最终影响相关器件的性能。通过归纳分析砷化镓单晶材料的本征特性及其切割、磨边、研磨、抛光等技术的研究进展,对砷化镓超光滑平坦化加工技术未来的研究方向进行展望。      

Oxidation of III-V semiconductors

This paper focuses on the characterization of anodic films (formed in aqueous electrolytes) and thermal oxides (formed at ∼500 °C) on GaAs, InP, AlGaAs, InAlAs, InAlP and heterostructures for GaAs- and InP-based devices. Emphasis is placed on Al-containing oxides, particularly on InAlP which possess good insulating properties. The composition and nature of the oxides have been determined by Auger electron spectroscopy, X-ray photoelectron spectroscopy, ¹⁶O/¹⁸O secondary ion mass spectrometry, Rutherford backscattering spectroscopy, scanning and transmission electron microscopy. Electrical measurements performed on metal-insulator-semiconductor (MIS) structures indicate that the Al-containing oxides have good electrical properties making the films potentially useful for some device applications.