A series of In0.36Ga0.64As/GaAs single quantum wells were grown by molecular beam epitaxy to investigate the dependence of the critical layer thickness (CLT) on growth temperature. The layers were grown between 410 and 590 °C. Photoluminescence was then used to determine the CLT as the onset of three-dimensional growth which occurs at 15 Å for 570 °C and at 55 Å when grown at 470 °C. Our results indicate a strong and nearly linear temperature dependence for the CLT.
Transition from two-dimensional to three-dimensional growth mode has been investigated by photoluminescence in highly strained InxGa1−xAs/GaAs (0.36≤x≤1) single quantum wells. The structures were grown by molecular beam epitaxy from 410 to 590 °C. The critical layer thickness based on this transition decreased as the growth temperature increased. This behavior was well described by the single-kink Matthews model [J. Vac. Sci. Technol. 12, 126 (1975)] including the simplest expression of the Peierls–Nabarro friction stress [J. Appl. Phys. 41, 3800 (1970)].
The strain mediation in multiple quantum well structures consisting of In0.36Ga0.64As layers separated by GaAs barriers has been investigated by photoluminescence. Strain in layers grown by molecular beam epitaxy was evaluated by comparing the photoluminescence-peak energies with calculated recombination energies in strained quantum wells using the effective-mass Schrödinger equation. In structures consisting of two 40 Å thick In0.36Ga0.64As layers separated by a GaAs barrier, onset of relaxation is not observed until the barrier thickness is reduced below 100 Å. The corresponding value is 180 Å in a structure with two 50 Å thick In0.36Ga0.64As layers. Results also show that strain mediation increases with the number of strained In0.36Ga0.64As layers. In multiple quantum well structures with four 50 Å thick In0.36Ga0.64As layers, the barrier thickness required to stop strain mediation increases to 225 Å. In similar structures with eight and twenty 50 Å thick In0.36Ga0.64As layers this value is 275 Å.
The desorption rate of In atoms from an InAs surface and its dependence on surface As coverage is reported. InAs films were grown by molecular beam epitaxy on fully strained 1 monolayer thick In0.75Ga0.25As films deposited on (001) InAs substrates. Using a sensitive technique based on reflection high-energy electron diffraction, the desorption rate for In is found to be highly dependent on the As coverage. During a sublimation process, where In from an InAs surface is desorbed, the desorption rate at 510 °C is five times greater for a group III stabilized surface than for an As-stabilized surface. The difference in desorption rate is believed to be related to changes in the In to surface bond strengths.
Hall measurements were made on selectively Si-doped InSb, GaSb/InSb, and GaAs/InSb heterostructures grown by molecular beam epitaxy using cracker sources. A cap layer had a pronounced influence especially on the low temperature conduction. The measurements showed an apparent increase in free carrier concentration and reduction of mobility due to compensation and/or parallel conduction. The best mobility, 38 700 cm2/V s at room temperature, was measured in a 2-μm-thick InSb layer capped with GaSb and doped with a concentration of 3×1016 cm−3 within 1000 Å from the cap interface. The variation of carrier concentration with temperature in doped samples revealed singularities at 50 and 90 K due to conduction from an unintentional p-background doping.
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