1.3 mu m high indium content (42.5%) GaInNAs/GaAs quantum wells grown by molecular beam epitaxy

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum well (QW) samples with 42.5% indium content were successfully grown by molecular beam epitaxy. The growth of well layers was monitored by reflection high-energy electron diffraction (RHEED). Room temperature photoluminescence (PL) peak intensity of the GaIn0.425NAs/GaAs (6 nm / 20 nm) 3QW is higher than, and the full width at half maximum (FWHM) is comparable to, that of In0.425GaAs/GaAs 3QW, indicating improved optical quality due to strain compensation effects by introducing N to the high indium content InGaAs epilayer. The measured (004) X-ray rocking curve shows clear satellite peaks and Pendellosung fringes, suggesting high film uniformity and smooth interfaces. The cross sectional TEM measurements further reveal that there are no structural defects in such high indium content QWs. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical properties of inGaAs/GaAs quantum wells grown by Sb-assisted molecular beam epitaxy

It is found that both methods using either continuous Sb supply or pre-deposition of a very thin Sb layer are efficient for the Sb-assisted molecular beam epitaxy growth of highly strained InGaAs/GaAs quantum wells (QWs). The emission of QWs is extended to long wavelength close to 1.25 mu m with high luminescence efficiency at room temperature. The influence of rapid thermal annealing (RTA) on the photoluminescence intensity critically depends on the annealing temperature and duration for highly strained QWs. A relatively low RTA temperature of 700 degrees C with a short duration of 10 s is suggested for optimizing the annealing effect. (c) 2005 Elsevier B.V. All rights reserved.

High Characteristic Temperature 1.3 mu m InAs/GaAs Quantum-Dot Lasers Grown by Molecular Beam Epitaxy

We report the molecular beam epitaxy growth of 1.3 mu m InAs/GaAs quantum-dot (QD) lasers with high characteristic temperature T-0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 mu m and a cavity length of 1200 mu m are fabricated and tested in the pulsed regime under different temperatures. It is found that T-0 of the QD lasers is as high as 532K in the temperature range from 10 degrees C to 60 degrees C. In addition, the aging test for the lasers under continuous wave operation at 100 degrees C for 72 h shows almost no degradation, indicating the high crystal quality of the devices.

Substrate temperature dependence of ZnTe epilayers grown on GaAs(001) by molecular beam epitaxy

ZnTe thin films have been grown on GaAs(0 0 1) substrates at different temperatures with constant Zn and Te beam equivalent pressures (BEPs) by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) observation indicates that two-dimensional (2D) growth mode can be established after around one-minute three-dimensional (3D) nucleation by increasing the substrate temperature to 340 degrees C. We found that Zn desorption from the ZnTe surface is much greater than that of Te at higher temperatures, and estimated the Zn sticking coefficient by the evolution of growth rate. The Zn sticking coefficient decreases from 0.93 to 0.58 as the temperature is elevated from 320 to 400 degrees C. The ZnTe epilayer grown at 360 degrees C displays the narrowest full-width at half-maximum (FWHM) of 660 arcsec from (0 0 4) reflection in double-crystal X-ray rocking curve (DCXRC) measurements. The surface morphology of ZnTe epilayers is strongly dependent on the substrate temperature, and the root-mean-square (RMS) roughness diminishes drastically with the increase in temperature.

Optimization of VI/II pressure ratio in ZnTe growth on GaAs(001) by molecular beam epitaxy

ZnTe epilayers were grown on GaAs(0 0 1) substrates by molecular beam epitaxy (MBE) at different VI/II beam equivalent pressure (BEP) ratios (R-VI/II) in a wide range of 0.96-11 with constant Zn flux. Based on in situ reflection high-energy electron diffraction (RHEED) observation, two-dimensional (2D) growth mode can be formed by increasing the R-VI/II to 2.8. The Te/Zn pressure ratios lower than 4.0 correspond to Zn-rich growth state, while the ratios over 6.4 correspond to Te-rich one. The Zn sticking coefficient at various VI/II ratios are derived by the growth rate measurement. The ZnTe epilayer grown at a R-VI/II of 6.4 displays the narrowest full-width at half-maximum (FWHM) of double-crystal X-ray rocking curve (DCXRC) for (0 0 4) reflection. Atomic force microscopy (AFM) characterization shows that the grain size enlarges drastically with the R-VI/II. The surface root-mean-square (RMS) roughness decreases firstly, attains a minimum of 1.14 nm at a R-VI/II of 4.0 and then increases at higher ratios. It is suggested that the most suitable R-VI/II be controlled between 4.0 and 6.4 in order to grow high-quality ZnTe epitaxial thin films.

High resistance AlGaAs/GaAs quantum cascade detectors grown by solid source molecular beam epitaxy operating above liquid nitrogen temperature

This work was supported by the National Research Projects of China (grant numbers are 60525406, 60736031, 60806018, 60906026, 2006CB604903, 2007AA03Z446 and 2009AA03Z403, 10990100, respectively). The authors would like to thank P Liang, Y Hu, H Sun, X L Zhang, B J Sun, H L Zhen and N Li for their help in processing and characterization.

Molecular beam epitaxy of GaSb on GaAs substrates with AlSb/GaSb compound buffer layers

GaSb films with AlSb/GaSb compound buffer layers were grown by molecular beam epitaxy on GaAs (001) substrates. The crystal quality and optical properties were studied by high resolution transition electron microscopy and low temperature photoluminescence spectra (PL), respectively. It was found that the AlSb/GaSb compound buffer layers can restrict the dislocations into GaSb epilayers. The intensity of PL spectra of GaSb layer becomes large with the increasing the periods of AlSb/GaSb superlattices, indicating that the optical quality of GaSb films is improved.

HIGH-QUALITY INGAP AND INGAP/INALP MULTIPLE-QUANTUM-WELL GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

Using gas-source molecular beam epitaxy, we have obtained high-quality GaInP and (AlGa)InP epilayers lattice-matched to (100) GaAs substrates. All grown layers exhibited mirror-like surfaces. For a 1.7 mum thick Ga0.5In0.5P film, the Hall electron mobility was 3400 and 30,000 CM2/V. s at 300 and 77 K, respectively. The luminescence wavelength of (AlxGa1-x)InP samples ranged from 680 nm (for GaInP) to 590 nm (for AlInP) at room temperature, and from 644 to 513 nm at 77 K. The multiple quantum well (MQW) structure with well width of 40 angstrom showed strong luminescence intensity with wavelength of 647 nm (300 K) or 622 nm (80 K). The satellite peaks can be detected in double-crystal X-ray (DCXR) diffraction measurements of the MQW samples, which indicates the perfect structural periodicity.

REDUCTION OF CRYSTALLINE DISORDER IN MOLECULAR-BEAM EPITAXY GAAS ON SI BY MEV ION-IMPLANTATION AND SUBSEQUENT ANNEALING

Molecular beam epitaxy GaAs films on Si, with thicknesses ranging from 0.9-2.0-mu-m, were implanted with Si ions at 1.2-2.6 MeV to doses in the range 10(15)-10(16) cm-2. Subsequent rapid infrared thermal annealing was carried out at 850-degrees-C for 15 s in a flowing N2 atmosphere. Crystalline quality was analyzed by using Rutherfold backscattering/channeling technique and Raman scattering spectrometry. The experimental results show that the recrystallization process greatly depends on the dose and energy of implanted ions. Complete recrystallization with better crystalline quality can be obtained under proper implantation and subsequent annealing. In the improved layer the defect density was much lower than in the as-grown layer, especially near the interface.

IMPLANTATION ENERGY SELECTION IN MOLECULAR-BEAM EPITAXY GAAS FILMS ON SI SUBSTRATES

GaAs films made by molecular beam epitaxy with thicknesses ranging from 0.9 to 1.25-mu-m on Si have been implanted with Si ions at 1.2 MeV to dose of 1 x 10(15)/cm2. A rapid infrared thermal annealing and white light annealing were then used for recrystallization. Crystalline quality was analysed by using backscattering channeling technique with Li ion beam of 4.2 MeV. The experimental results show that energy selection is important for obtaining better and uniform recrystallized GaAs epilayers.

CONVERGENT-BEAM ELECTRON-DIFFRACTION STUDY OF GE0.5SI0.5/SI STRAINED-LAYER SUPERLATTICES GROWN BY MOLECULAR-BEAM EPITAXY

Side bands due to purely composition and combined composition-strain modulation in plan-view specimens of a nominally Ge0.5Si0.5(5nm)/Si(25nm) superlattice have been obtained by large-angle convergent-beam electron diffraction. The intensities of the side bands have been calculated from a periodic tension-compression model of the superlattice bilayer using the kinematical theory of electron diffraction. Accurate values of elastic strains in the bilayer and of the Ge content can be obtained in this way.

Ge composition saturation behavior during low-temperature Si1-xGex growth by disilane and solid Ge molecular beam epitaxy

Ge composition dependence on the Ge cell temperature has been studied during the growth of Si1-xGex by disilane and solid Ge molecular beam epitaxy at a substrate temperature of 500 degrees C. It is found that the composition x increases and then saturates when the Ge cell temperature increases, which is different from the composition-dependent behavior in growth at high temperature as well as in growth by molecular beam epitaxy using disilane and germane. The enhanced hydrogen desorption from a Ge site alone cannot account for this abnormal composition-variation behavior. We attribute this behavior to the increase of rate constant of H desorption on a Si site when the Ge cell temperature increases.