Incorporation of silicon and aluminum in low temperature molecular beam epitaxial GaAs (original) (raw)
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Semiconductors, 1997
The results of an investigation of the structural perfection of GaAs epitaxial films grown by molecular-beam epitaxy at low growth temperatures ͑240-300°C͒ and various As/Ga flux ratios ͑from 3 to 13͒ are presented. Diffraction reflection curves display characteristic features for the samples before and after annealing in the temperature range from 300 to 800°C. Hypotheses which account for these features are advanced. The range of variation of the arsenic/ gallium flux ratio, in which low-temperature growth takes place under nearly stoichiometric conditions, is established.
The role of As in molecular-beam epitaxy GaAs layers grown at low temperature
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1991
Annealed GaAs layers grown at low temperatures (180-300 •C) by molecular-beam epitaxy (MBE) were studied by transmission electron microscopy (TEM). These layers were used as buffers for a field-effect transistor (PET) device structure and effectively eliminated sidegating effects. All these layers were found to contain As precipitates. Precipitate size and separation between them differed from sample to sample. The smallest precipitates were coherent "pseudocubic." Larger precipitates had hexagonal structure. The distance between precipitates was estimated to be in the range of 10-40 nm. These results are consistent with the buried Schottky model by Warren et ai., although other explanations cannot be excluded at present.
MRS Proceedings, 1989
Using SIMS profiling, temperature-dependent Hall measurements, electronic Raman scattering, and infra-red absorption, a detailed study is presented examining the effects of Si dopant behaviour on intersubband absorption in GaAs/Al .32Ga .68As MQW’s. The samples were grown by molecular beam epitaxy at substrate temperatures ranging from 520 to 680°C with Si doping in the GaAs quantum wells only. SIMS profiling reveals that, with increasing substrate temperature, substantial Si migration into the Al .32Ga.68 As barrier layers occurs during epitaxial growth. Hall measurements indicate that both at elevated growth temperatures and under reduced incident As4 beam fluxes, the electron sheet concentration is reduced in the QW’s. In both cases, loss of free carriers is attributed to enhanced Si compensation. Shifts in the absolute frequency of the infra-red absorption resonance, determined by electronic Raman scattering, as well as variations in the integrated absorption intensity, are both...
Deep levels in GaAs grown by atomic layer molecular beam epitaxy
Applied Physics Letters, 1994
We present a study on deep levels in GaAs:Si grown by atomic layer molecular beam epitaxy ALMBE. We show that in ALMBE GaAs grown at temperatures T S in the range 370-530°C, the deep level concentrations: i are up to 3 orders of magnitude smaller than those of material grown by molecular beam epitaxy MBE at similar temperature ranges, and ii can be compared to those of GaAs grown by MBE at 600°C. These features are independent whether Si is supplied during: a both the Ga and As subcycles, b the As subcycles, or c the Ga subcycles. Therefore, as for deep levels, ALMBE GaAs grown at 370T S 530°C can be related to GaAs prepared by MBE at conventional temperatures.
Journal of Crystal Growth, 2001
Optimized MBE outgassing procedures eliminated Hillock-type oval defects, allowing the bonding of epitaxial GaAs/ AlGaAs wafers with Si wafers. The application of a single growth epitaxial structure for the fabrication of laser diode (LD) and photodetector (PD) devices was investigated. Four graded index separate confinement heterostructure-multiquantum well (GRINSCH-MQW) LD structures with 2, 4, 8 and 16 GaAs quantum wells (QWs) were used to evaluate quantitatively the effect of the number of QWs in the performance of LDs. Threshold current density values of 358 A/ cm 2 for 2 QWs, 484 A/cm 2 for 4 QWs, 685 A/cm 2 for 8 QWs and 1435 A/cm 2 for 16 QWs were measured. PDs were fabricated by five GRINSCH-MQW structures with 2-32 QWs and exhibited responsivity of 0.020 A/W for 2 QWs, 0.031 A/W for 4 QWs, 0.069 A/W for 8 QWs, 0.181 A/W for 16 QWs and 0.350 A/W for 32 QWs. #
Journal of Applied Physics, 1997
We have investigated the structural and defect characteristics of GaAs and Al x Ga 1Ϫx As grown at low substrate temperature ͑250°C͒ by molecular beam epitaxy. Using x-ray diffraction we have observed an increase in lattice parameter for all as-grown layers, with the Al x Ga 1Ϫx As layers showing a smaller expansion than the GaAs layer. However, infrared absorbtion measurements revealed that the concentration of neutral arsenic antisite defect, ͓As Ga ͔ 0 , was not significantly affected by aluminum content (x), with only a small reduction for xϭ0.36. Positron beam studies showed that the low temperature layers had a higher concentration of vacancy-related defects ͑ϳ10 17 cm Ϫ3 ͒ than the semi-insulating substrate, with the Al x Ga 1Ϫx As layers having the highest values. After annealing ͑600°C, 15 min͒ the lattice constants relaxed to those of conventionally grown material and ͓As Ga ͔ 0 was reduced in all cases, with the smallest reduction occurring for the xϭ0.36 layer, indicating that the Al atoms strengthen the lattice against excess arsenic incorporation and hold the arsenic antisite atoms more strongly in position. X-ray photoelectron spectroscopy showed that arsenic diffused out of the surface region and was replaced by oxygen, possibly due to an insufficient overpressure of forming gas during the anneal. This oxygen penetration was greater for the GaAs layer than for the Al x Ga 1Ϫx As layers. Extra Raman peaks at 200 and 257 cm Ϫ1 confirmed that the surface was very disordered. There was, nevertheless, a large increase ͑4%͒ in the positron S parameter in the bulk of the annealed layers, suggesting the formation of vacancy clusters, whereas in the surface region we find evidence that As Ga diffusion proceeded at a faster rate in the xϭ0.36 than the xϭ0.2, in agreement with the vacancy-enhanced As Ga diffusion model.
Molecular beam epitaxy growth of AlGaAs on the (631)-oriented GaAs substrates
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2008
The authors report the molecular beam epitaxy growth and characterization of AlGaAs/ GaAs͑631͒ heterostructures grown at different As 4 molecular beam equivalent pressures. The reflection high-energy electron diffraction patterns taken along the ͓−1 2 0͔ azimuth showed that the twofold reconstruction commonly observed during the GaAs-buffer layer growth is preserved during the AlGaAs deposition. The 10 K photoluminiscence ͑PL͒ characterization of the samples showed transitions related to the AlGaAs band edge, the incorporation of impurities, and deep centers. The temperature dependence of the band to band PL transition was fitted with the models developed by Varshni, Pässler, and Viña. The intensity of the PL spectra drastically decreases as the As 4 pressure is increased. Photoreflectance ͑PR͒ spectroscopy also showed the best crystal quality for the sample grown at low As pressure. The authors obtained the built-in internal electric field strength and the band-gap energy from an analysis of the PR spectra close to the GaAs band edge employing the Franz-Keldysh model.
A study of Al/Si3N4/ultrathin Si/GaAs structures by DLTS and C–V measurements
Thin Solid Films, 2003
We present a study on electrical properties of AlySi N ySiyGaAs structure studied by deep level transient spectroscopy and 3 4 capacitance-voltage technique. Here, the Si means an ultrathin silicon layer with thickness of approximately 2 nm. We have modelled the presented structure, while emissions from deep levels at SiyGaAs interface, traps in the bulk of GaAs and from a quantum well (QW) possibly formed by the Si interlayer, were taken into the account. Four deep traps were identified in the structure with the following thermal activation energies: 0.04, 0.19, 0.40 and 0.68 eV. The energy levels 0.4 and 0.68 are related with As defects, while the energy levels 0.04 and 0.19 are associated with the presence of the Si interlayer. Based on the emission behaviour, an existence of the QW is not probable (can be excluded). Rather, parameters of the Si-related energy levels suggest the levels are induced by d-doping of GaAs. ᮊ
Local vibrational properties of GaAs studied by extended X-ray absorption fine structure
The Journal of Chemical Physics, 2013
Extended X-ray absorption fine structure (EXAFS) has been measured at both the K edges of gallium and arsenic in GaAs, from 14 to 300 K, to investigate the local vibrational and thermodynamic behaviour in terms of bond expansion, parallel, and perpendicular mean square relative displacements and third cumulant. The separate analysis of the two edges allows a self-consistent check of the results and suggests that a residual influence of Ga EXAFS at the As edge cannot be excluded. The relation between bond expansion, lattice expansion, and expansion due to anharmonicity of the effective potential is quantitatively clarified. The comparison with previous EXAFS results on other crystals with the diamond or zincblende structure shows that the values of a number of parameters determined from EXAFS are clearly correlated with the fractional ionicity and with the strength and temperature interval of the lattice negative expansion. © 2013 AIP Publishing LLC.