Role of Al content on surface structure evolution of low temperature AlxGa1−xAs and its effect on critical thickness

Abstract

Low temperature sapphire nitridation: A clue to optimize GaN layers grown by molecular beam epitaxy J. Appl. Phys. 85, 1550 (1999; 10.1063/1.369286 Molecular beam epitaxial growth of InAs/AlGaAsSb deep quantum well structures on GaAs substrates Reflection high energy electron diffraction ͑RHEED͒ has been used to track the evolution of both low temperature ͑LT͒ GaAs and LT-Al x Ga 1Ϫx As growth surfaces. LT-Al x Ga 1Ϫx As surfaces have been found to roughen by a pyramidal defect formation similar to that reported for LT-GaAs over the entire range of aluminum compositions. Correlations between RHEED and transmission electron microscopy ͑TEM͒ results indicate that the critical thickness found using the formation of extra fourth order diffraction spots as a marker correlate well to the nucleation of pyramidal defects. Additionally, results for the critical thickness of layers grown over the range of aluminum compositions indicate an exponential decrease in the critical thickness with increasing aluminum composition under similar growth conditions. While the mechanism for this dependence is still unclear, it does not appear to be related to an increase in the excess arsenic incorporation with increasing Al composition.

Single-valley high-mobility (110) AlAs quantum wells with anisotropic mass

“…We assume that the AlAs QW (a AlAs = 5.65252 A) is strained relative to the GaAs substrate lattice (a GaAs = 5.64177Å) in agreement with previous publications. 13,14,15 For (110) biaxial strain, the perpendicular component can be deduced from the in-plane strain as ǫ ⊥ = −D · ǫ || , where D = 0.6165 is a constant that depends on the interface orientation and on the elastic constants of AlAs. 13,16 In the growth-basis a, (0, b, 0) is the growth direction, and the strain tensorǭ ij is diagonal withǭ aa =ǭ zz = ǫ || , andǭ bb = ǫ ⊥ .…”