Broadening factor due to electron–phonon collisions in semiconductor quantum wells

Abstract

Electron–phonon collisions result in finite relaxation time and energy shift of electron’s states in semiconductors. These effects make the optical line shape broadened and shift its peak position. Hence these two quantities play an important role in semiconductor optical devices absorption spectrum. Here a theoretical model is presented to calculate the broadening factor and energy shift resulting from the interactions of phonons and two-dimensional electrons, including intra- and intersub-band processes. In this model, taken into account are the effective-mass discontinuity and finite barrier height for electron wave functions in order to derive exact momentum selection function of electron–phonon interactions. Due to the steplike nature of two-dimensional density of states, the broadening factor also appears steplike and strongly energy dependent. The influences of carrier density, temperature, and well width are also discussed.