Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities

Abstract

We calculate the intersubband absorption linewidth 2Γ op in quantum wells(QWs) due to scattering by interface roughness, LO phonons, LA phonons, alloy disorder, and ionized impurities, and compare it with the transport energy broadening 2Γ tr =2ℏ/τ tr , which corresponds to the transportrelaxation time τ tr related to the electron mobility μ. Numerical calculations for GaAs QWs clarify the different contributions of each individual scattering mechanism to the absorption linewidth 2Γ op and transport broadening 2Γ tr . Interface roughnessscattering contributes about an order of magnitude more to the linewidth 2Γ op than to the transport broadening 2Γ tr , because the contribution from the intrasubband scattering in the first excited subband is much larger than that in the ground subband. On the other hand, LO phononscattering (at room temperature) and ionized impurity scattering contribute much less to the linewidth 2Γ op than to the transport broadening 2Γ tr . LA phononscattering makes comparable contributions to the linewidth 2Γ op and transport broadening 2Γ tr , and so does alloy disorder scattering. The combination of these contributions with significantly different characteristics makes the absolute values of the linewidth 2Γ op and transport broadening 2Γ tr very different, and leads to the apparent lack of correlation between them when a parameter, such as temperature or alloy composition, is changed. Our numerical calculations can quantitatively explain the previously reported experimental results.