Degradation of InGaAs High Electron Mobility Transistors: The Role of Channel Composition and Thickness

Abstract

AbstractIn this study, we examined the performance of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors with varying channel layer thicknesses for indium mole fractions of 0.21 and 0.24. For both compositions, we find that there is an optimum channel thickness above which the device performance is impaired. As expected the effective critical thickness of the In0.2iGa0.79As layer is higher. Surprisingly, however, transmission electron microscopy of the device structures indicates that the device performance is not impaired by the presence of a linear array of misfit dislocations. In fact, the devices with highest performance have misfit dislocations indicating that defect engineering may lead to improved performance in these structures. Furthermore, we find that device structures with poor performance have misfit dislocations along both of the <110> directions. Triple axis x-ray diffraction provides a non-destructive estimate of the dislocation densities present.