Calculation of strain distributions in multiple-quantum-well strained-layer structures

Abstract

We present a simple method for calculating strain distributions in structures containing an arbitrary number and combination of strained layers of finite length buried in an infinite medium. This method is used to calculate the strain distributions for a quantum-well stack containing four compressive layers separated by barriers of different thicknesses and states of strain. It is found that the in-plane strain is relaxed along a significant length of each compressive layer if the barriers are unstrained. In contrast, if the barriers are in tension, the compressive strain is retained over most of the length of the layer. It is concluded that the judicial use of compressive and tensile layers in device structures would substantially reduce the region over which the strain is relaxed and possibly minimize the adverse effects of modified band structure or atomic diffusion arising due to the relaxation of strain. It is also confirmed that strain relaxation reduces the average strain within the square cross section of a single quantum wire to about one tenth of the misfit strain.