Electronic scattering in doped finite superlattices

Abstract

The electronic scattering and momentum relaxation times for the individual levels in finite short-period modulation-doped superlattices were calculated, using the random phase approximation (RPA) to describe the screened electron-defect interactions. To obtain the highest possible electronic mobility, the donor impurities were placed in the middle of the barriers separating the wells. If the impurities are displaced from their ideal positions, the electronic mobility decreases. To evaluate the theory, measurements of the scattering and momentum relaxation times were done on ${\mathrm{I}\mathrm{n}\mathrm{P}/\mathrm{I}\mathrm{n}}_{0.53}{\mathrm{Ga}}_{0.47}\mathrm{As}$ superlattices. Whereas theory and experiment agree fairly well on the values of the scattering times, the agreement on the momentum relaxation times is only in order of magnitude. This is attributed to the inexactness of the screened potential in the RPA at short distances from the scattering centers.