Impact of strain on the band offsets of important III–V quantum wells: InxGa1−xN/GaN, GaAs/InxGa1−xP and InxGa1−xAs/AlGaAs

Lattice strain has immense effect on the optoelectronic properties of III–V semiconductor quantum wells (QWs), since it introduces a pronounced change on the band properties of QWs and it is often purposefully introduced to improve device performance. In this paper we report the results of our experimental and theoretical studies on, how the important parameter, the band offset, changes with strain for InxGa1−xN/GaN, GaAs/InxGa1−xP and InxGa1−xAs/AlGaAs QWs. Experimentally the band offsets have been studied through capacitance transient measurements in the form of deep level transient spectroscopy (DLTS) on suitable QWs within a Schottky diode. The energy levels in a QW are considered to be analogous to a deep trap in the forbidden energy gap. From detailed balance between the emission and capture, Arrhenius type expressions were derived to analyze transient emission data, from which the band offsets were computed. Theoretically the band positions at the heterointerfaces have been calculated from the equations developed, which directly correlate the position of the bands with the strain at the interface. The strain is calculated from the In mole fractions and lattice constants. The parameters implicitly involved are the elastic stiffness constants (C11 and C12), the hydrostatic deformation potential of the conduction band (a′), the hydrostatic deformation potential (a) and the shear deformation potential (b) for the valance band. The results should be useful to research workers in the field of optoelectronics.