Intrinsic electron mobilities in CdSe, CdS, ZnO, and ZnS and their use in analysis of temperature-dependent Hall measurements

Abstract

Intrinsic electron mobilities and intrinsic Hall r factors for n-type wide band gap II–VI semiconductors CdSe, CdS, ZnO, and ZnS are predicted from 60 to 400 K using the relaxation-time approximation including scattering due to polar-optical phonons and acoustic phonons (piezoelectric and deformation potentials). Experimental deformation potentials (E1) are used and the relative importance of deformation-potential scattering in these II–VI compounds is clarified. At 300 K, intrinsic Hall electron mobilities (in cm2/V s) are about 600 (CdSe), 440 (CdS), 230 (ZnO), and 250 (ZnS). The intrinsic predictions are applied to fitting of temperature-dependent Hall effect measurements from n-type CdSe, CdS, and ZnO bulk crystals including extrinsic scattering due to both neutral and ionized impurities. Donor and acceptor concentrations and activation energies are obtained, and Coulomb screening is included to yield donor ionization energies for isolated centers. The intrinsic mobility predictions establish upper limits for these compounds, especially important for thin film studies where sample inhomogeneities can produce anomalously high results.