Analysis of strain relaxation in GaAs∕InGaAs∕GaAs structures by spectroscopy of relaxation-induced states

Abstract

Strain relaxation in GaAs∕In0.2Ga0.8As∕GaAs structures is investigated by analyzing relaxation-induced traps. Strain relaxation is shown to cause carrier depletion by the induction of a 0.53eV trap in the top GaAs layer, a 0.13eV trap in the InGaAs layer, and a 0.33eV trap in the neighboring lower GaAs layer. The 0.53eV trap which exhibits a logarithmic function of transient capacitance is attributed to threading dislocations. The 0.33eV trap exhibits an exponential transient capacitance, suggesting a GaAs point defect as its origin. Given its activation energy, it is assigned to the EL6 in GaAs, commonly considered to be Asi-VGa complexes. This trap and the 0.13eV trap are regarded as the same, since their energy difference is comparable to the optically determined conduction-band offset. The spatial location of this trap correlates with that of misfit dislocations. Accordingly, the production of this trap is determined from the mechanism of strain relaxation. A likely mode of strain relaxation is deduced from the locations of these traps.