Conduction-band offsets in pseudomorphic InxGa1−xAs/Al0.2Ga0.8As quantum wells (0.07≤x≤0.18) measured by deep-level transient spectroscopy

Abstract

The variation of the potential of a quantum well is similar to that of a deep trap. In that respect a quantum well can capture and emit carriers in much the same way as a trap. The thermal emission energy from a quantum well is closely related to the appropriate band offset. With that in mind, we have carried out deep-level transient spectroscopy measurements on Schottky-barrier diodes containing one or more pseudomorphic ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/${\mathrm{Al}}_{0.2}$ ${\mathrm{Ga}}_{0.8}$As (0<x≤0.18) quantum wells. The objective was to estimate the conduction-band offset, Δ$E_c$, as a function of x and the resulting strain. From detailed balance between emission and capture, an Arrhenius-type expression was derived to analyze the transient emission data. It is seen that the percentage band offset Δ$E_c$/Δ$E_g$ varies from 62% for x=0.07 to 70% at x=0.18. Furthermore, a linear interpolation of the data leads to Δ$E_c$/Δ$E_g$=58% at x=0, which is close to the widely accepted value. Our results support recent theoretical calculations from which a monotonic increase in Δ$E_c$ with strain in this heterostructure system is predicted.