Multiple quantum well structures and high-power lasers of gaas- algaas grown by metalorganic vapor phase epitaxy (MOVPE)1

GaAs/AlGaAs GRIN-SCH type multiple quantum well lasers with four wells of 11 nm GaAs, grown in an MOVPE chimney reactor, exhibit an output power as high as 110 mW/facet (CW, 30°C; 5 μm stripe) and 1.3 W/facet (pulsed, 30°C; 53 μm stripe) until catastrophic optical damage occurs. 2000 hours life tests conducted at 60°C and 15 mW CW show no noticeable degradation for the 5 μm stripe laser with a reflective coating on both facets. Raman spectroscopy on similar multiple quantum well structures with 65 GaAs wells is used to ascertain that the wells have minimum residual aluminum- content.     

Free-standing and vertically aligned InP nanowires grown by metalorganic vapor phase epitaxy

Metalorganic vapor phase epitaxial technique has been used to grow surface mounted vertical and uniform cross-sectional InP nanowires on a wafer scale basis. The growth was carried out under the vapor–liquid–solid mechanism using Au colloidal nanoparticles of nominal diameters of 10 and 20 nm, and their properties were compared. The effect of the pre-growth anneals and growth temperatures on the stability of the nanowires were studied in detail. Scanning electron microscopy and transmission electron microscopic studies showed average diameter of the nanowires in the range of 20–35 nm, and of length 700 nm with growth direction of 1 1 1. Room temperature photoluminescence measurements of the nanowires grown on 10 and 20 nm Au particles showed strong peaks, which were blue shifted by 25 and 32 meV, respectively, compared to bulk InP.     

InGaAsP multiple quantum well edge-emitting light-emitting diode showing low coherence characteristics using selective-area metalorganic vapor phase epitaxy

Low coherence multiple-quantum well edge-emitting light-emitting diodes were obtained using selective-area metalorganic vapor-phase epitaxial growth, which utilized growth rate enhancement on an open stripe region between mask stripes. An optical absorption region, which was controlled by selective-area growth, was introduced to suppress optical feedback. At a driving current of 100 mA and an ambient temperature of 25°C, a power of 55 μW was coupled into a single-mode fiber, and a broad spectrum without spectral ripple was observed. Low coherence characteristics and very small temperature dependence were obtained in the temperature range from -40°C to 85°C. The modulation bandwidth was 210 MHz at a bias current of 100 mA.     

Operational and design considerations for broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition for high power applications

Graded barrier quantum well heterostructure (GBQWH) broad area lasers have been shown to be capable of high power pulsed and cw operation. In this article, we consider several operational characteristics and design issues associated with broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition. In particular, the effect of junction heating on emission wavelength for cw device operation and the effects of various buffer layer structures on the material properties and device characteristics of GBQWH structures are addressed. Typical results for high power operation of uncoated broad area laser diodes are also outlined.     

Operational and design considerations for broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition for high power applications

Graded barrier quantum well heterostructure (GBQWH) broad area lasers have been shown to be capable of high power pulsed and cw operation. In this article, we consider several operational characteristics and design issues associated with broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition. In particular, the effect of junction heating on emission wavelength for cw device operation and the effects of various buffer layer structures on the material properties and device characteristics of GBQWH structures are addressed. Typical results for high power operation of uncoated broad area laser diodes are also outlined.     

Thermodynamic analysis of the shape, anisotropy and formation process of InAs/InP(0 0 1) quantum dots and quantum sticks grown by metalorganic vapor phase epitaxy

This study describes the origin of the size and shape anisotropy of InAs/InP(0 0 1) quantum dots (QDs) grown by metalorganic vapor phase epitaxy (MOVPE). The geometry of the QDs is determined by carefully analyzing transmission electron microscopy (TEM) images. An analytical model adapted to our QD geometry is used to understand the formation mechanism of the QDs, and to describe the origin of their size dispersion. A shape transition from QDs to elongated quantum sticks (QS) is observed under As-poor growth conditions. This transition, driven by thermodynamics, is clearly described by our model.     

Self-assembled InAs island formation on GaAs (1 1 0) by metalorganic vapor phase epitaxy

Formation of self-assembled InAs 3D islands on GaAs (1 1 0) substrate by metal organic vapor phase epitaxy has been investigated. Relatively uniform InAs islands with an average areal density of 10⁹ cm⁻²are formed at 400 ° C using a thin InGaAs strain reducing (SR) layer. No island formation is observed without the SR layer. Island growth on GaAs (1 1 0) is found to require a significantly lower growth temperature compared to the more conventional growth on GaAs (1 0 0) substrates. In addition, the island height is observed to depend only weakly on the growth temperature and to be almost independent of the V/III ratio and growth rate. Low-temperature photoluminescence at 1.22 eV is obtained from the overgrown islands.     

Tellurium delta‐doped InGaP layers grown by metalorganic vapour phase epitaxy

Heavily n‐type doped and several nanometres thick In_0.485Ga_0.515P layers are necessary for various devices. We studied the delta‐doping of this ternary with tellurium; the layers were grown by metalorganic vapour phase epitaxy (MOVPE), and diethyltelluride was used as the precursor. A maximum Hall sheet concentration of 2.75 × 10¹³ cm^–2 was achieved in our samples grown at 560 °C. The Te profiles were analyzed with secondary ion mass spectrometry (SIMS), and a very narrow spectrum with a full width at half maximum of 7.5 nm was measured. This value indicates that the memory effect, referred to in the literature, was practically eliminated with appropriate growth conditions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multiple quantum well mixing and index-guided quantum well heterostructure lasers by MeV ion implantation

In recent years considerable interest has been shown in impurity-induced compositional disordering of III–V compound semiconductor devices, especially in efforts directed towards fabricating index-guided buried heterostructure lasers and other unique photonic and electronic devices. In this work we describe the study of compositional disordering induced by MeV implantation of oxygen and krypton into AlAs-GaAs superlattices and the fabrication of index-guided quantum well heterostructure lasers by MeV oxygen ion implantation.     

Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy

A route towards optimisation of uniformity and density of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V/III ratio, a fact which was shown to be valid when either AsH₃ (arsine) or tertiary-butyl-arsine (TBA) were used as group V precursors. Once the optimum V/III ratio was found, the size distribution was further improved by adjusting the nominal thickness of deposited InAs material, resulting in an optimum thickness of 1.8 monolayers of InAs in our case. The number of coalesced dots was minimised by adjusting the growth interruption time to approximately 30 s. Further, the uniformity was improved by increasing the growth temperature from 485 °C to 520 °C. By combining these optimised parameters, i.e. a growth temperature of 520 °C, 1.8 monolayers InAs thickness, 30 s growth stop time and TBA as group V precursor, a full-width-half-maximum (FWHM) of the low temperature luminescence band of 40 meV was achieved, indicating a narrow dot size distribution.     

Influence of growth parameters on the properties of InGaN/GaN multiple quantum well grown by metalorganic chemical vapor deposition

The effects of growth parameters such as barrier growth time, growth pressure and indium flow rate on the properties of InGaN/GaN multiple quantum wells (MQWs) were investigated by using photoluminescence (PL), high resolution X-ray diffraction (HRXRD), and atomic force microscope (AFM). The InGaN/GaN MQW structures were grown on c-plane sapphire substrate by using metalorganic chemical vapor deposition. With increasing barrier growth time, the PL peak energy is blue-shifted by 18 nm. For InGaN/GaN MQW structures grown at different growth pressures, the PL intensity is maximized in the 300 Torr – grown structure, which could be attributed to the improved structural quality confirmed by HRXRD and AFM results. Also, the optical properties of InGaN/GaN MQW are strongly affected by the indium flow rate.     

EPR measurement on Er-doped InP grown by organometallic vapor phase epitaxy

We have performed X-band ESR measurements on InP:Er epitaxial layers grown by organometallic vapor phase epitaxy, which were grown at the substrate temperatures of 530°C (sample A) and 580°C (sample B). Sample A shows a slightly anisotropic resonance aroundg = 6 with hyperfine structure due to the¹⁶⁷Er (I = 7/2) isotope at 3 K. This result is similar to the result for Erdoped bulk InP and it indicates that Er³⁺ ions are located in In tetrahedral sites. On the other hand, we do not see such a resonance for sample B, suggesting that the local symmetry of Er in sample B is different from sample A. The difference between samples A and B is consistent with the fluorescence-detected extended X-ray absorption fine structure results that the coordination number of Er depends on the growth temperature.     

Features of an InAsSbP epilayer formation on an InAs support by metalorganic vapor phase epitaxy

Epitaxial layers in a system of InAs_1–x–ySb_yP_x solid solutions in the composition range of 0 < x < 0.72 were obtained on an InAs(001) substrate by metalorganic vapor phase epitaxy (MOVPE). The layer-by-layer analysis of obtained structures by secondary ion mass spectrometry showed a gradient change in the composition along the growth direction. A dramatic change in the composition at the layer/substrate heteroboundary was observed for the quaternary InAsSbP solid solutions due to the presence of radicals of arsenic compounds in the gas phase. Upon MOVPE deposition on the InAs substrate in a system of InAsSbP solid solutions, the decrease in the solid-phase content of arsenium by less than (1–x–y) < 0.3 resulted in a suppression of the deposited layer gradientness, as well as suppressed fluctuations in the composition in the initial transition layer.     

Porous AlN films grown on C-face SiC by hydride vapor phase epitaxy

We report the growth of porous AlN films on C-face SiC substrates by hydride vapor phase epitaxy (HVPE). The influences of growth condition on surface morphology, residual strain and crystalline quality of AlN films have been investigated. With the increase of the V/III ratio, the growth mode of AlN grown on C-face 6H-SiC substrates changes from step-flow to pit-hole morphology. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman analysis show that cracks appear due to tensile stress in the films with the lowest V/III ratio and the highest V/III ratio with a thickness of about 3 μm. In contrast, under the medium V/III ratio growth condition, the porous film can be obtained. Even when the thickness of the porous AlN film is further increased to 8 μm, the film remains porous and crack-free, and the crystal quality is improved.     

Fabrication of p-CuGaS2/n-ZnO:Al heterojunction light-emitting diode grown by metalorganic vapor phase epitaxy and helicon-wave-excited-plasma sputtering methods

Greenish-white electroluminescence (EL) was observed from the heterojunction light-emitting diodes (LEDs) composed of p-type (001) CuGaS₂ chalcopyrite semiconductor epilayers and preferentially (0001)-oriented polycrystalline n-type ZnO thin films. The CuGaS₂ layers were grown on a (001) GaP substrate by metalorganic vapor phase epitaxy and the ZnO films were deposited by the surface-damage-free helicon-wave-excited-plasma sputtering method. The n-ZnO/p-CuGaS₂ LED structure was designed to enable an electron injection from the n-type wider band gap material forming a TYPE-I heterojunction. The EL spectra exhibited emission peaks and bands between 1.6 and 2.5 eV, although their higher energy portions were absorbed by the GaP substrate. Since the spectral lineshape resembled that of the photoluminescence from identical CuGaS₂ epilayers, the EL was assigned to originate from p-CuGaS₂.     

The beam properties of high-power InGaAs/AlGaAs quantum well lasers

The vertical beam quality factor of the fundamental TE propagating mode for InGaAs/AlGaAs SCH DQW lasers emitting at 940 nm is investigated by using the transfer matrix method and the non-paraxial vectorial moment theory for non-paraxial beams. An experimental approach is given for the measurement of the equivalent vertical beam quality factor of an InGaAs/AlGaAs SCH DQW laser. It has been shown that the vertical beam quality factor M_x² is always larger than unity, whether the thickness of the active region of LDs is much smaller than the emission wavelength or not.     

分子束外延生长的(GaAs1－xSbx/InyGa1－yAs)/GaAs量子阱光致发光谱研究

报道了(GaAs_1-xSb_x/In_yGa_1-yAs)/Ga As量子阱结构的分子束外延生长与光致发光谱研究结果.变温与变激发功率光致发光谱的研究表明了此结构 为二型量子阱发光性质.讨论了光谱双峰结构的跃迁机制.通过优化生长条件，获得了室温1 31μm发光. 关键词： 分子束外延 量子阱 二型发光     

Laser reflectometry in situ monitoring of InGaAs grown by atmospheric pressure metalorganic vapour phase epitaxy

InGaAs layers on undoped GaAs (0 0 1) substrates were grown by atmospheric pressure metalorganic vapour phase epitaxy (AP-MOVPE). In order to obtain films with different indium composition (x_In), the growth temperature as a growth parameter, was varied from 420 to 680 °C. Furthermore, high-resolution X-ray diffraction (HRXRD) measurements were used to quantify the change of x_In. Crystal quality has been also studied as a function of growth conditions. On the other hand, laser reflectometry (LR) at 632.8 nm wavelength, was employed to in situ monitor epitaxy. Reflectivity-time signal was enabled to evaluate structural and optical properties of samples. We have fitted experimental data to determine optical constants and growth rate of InGaAs at 632.8 nm. In addition, the fitting provided InGaAs thickness as a function of growth time. Based on ex situ characterization by scanning electronic microscopy (SEM) and HRXRD, we propose a practical method, relating the contrast of first reflectivity maximum with the X-ray diffraction peak angular difference between the substrate and epitaxial layer, to determine in situ the In solid composition in InGaAs alloys.     

Surface morphology of GaN nanorods grown by catalyst-free hydride vapor phase epitaxy

GaN nanorods were grown on c-plane sapphire substrates by using catalyst-free hydride vapor phase epitaxy (HVPE). The effects of substrate temperature, Ga boat temperature, and Ga pretreatment on the surface morphology of GaN nanorods were investigated. From the dependence of a radial and axial growth rate on the substrate temperature, the kinetically limited process was found to be a rate determining step in the growth of GaN nanorods in HVPE. In addition, the activation energy of the growth along the both axial and radial directions were estimated. The dependence of a Ga boat temperature and the Ga pretreatment effect revealed that the density of nanorods were dependent on the flux of Ga species on the substrate.