Highly anisotropic electron mobilities of GaAs/In0.2Ga0.8As/Al0.3Ga0.7As inverted high electron mobility transistor structures

Abstract

Anisotropic electron mobilities for GaAs/In0.2Ga0.8As/Al0.3Ga0.7As inverted high electron mobility transistor structures were observed using Hall effect measurements. If the In0.2Ga0.8As quantum-well thickness is below the critical layer thickness, a higher electron mobility in the 〈01–1〉 direction is observed in comparison to the 〈011〉 direction. Exceeding the critical layer thickness of the In0.2Ga0.8As quantum well results in a change in the behavior of the anisotropy, and a highly anisotropic electron mobility with a higher electron mobility in the 〈011〉 direction, in comparison to the 〈01–1〉 direction, is observed. With increasing In0.2Ga0.8As quantum-well width, the anisotropy increases. An increase of the anisotropy was also observed if the Hall-effect measurements were carried out at lower temperatures. The anisotropy in the electron mobility can be correlated to the occurrence of a highly asymmetric-dislocation density. The asymmetry in the dislocation density was observed using wavelength-selective catholuminescence measurements.