CHARGE TRANSFER AND ELECTRON MOBILITY IN GAALAS/GAAS MODULATION-DOPED HETEROSTRUCTURES - THE ROLE OF INTERFACE STATES

摘要

We develop a theoretical model of charge equilibrium in modulation-doped GaAlAs/GaAs heterojunctions in which the presence of donor-like interface states is considered, Assuming that the electrons occupy the first and second electronic subbands we calculate the charge transfer in the heterojunction as a function of the temperature, taking into account the metastable character of the Si donors in the GaAlAs-doped layer. We show that interface states, the density of which depends on the growth process and on the sample quality, play an important role in the temperature dependence of the charge equilibrium and allow us to explain the variation of the density of the 2D electrons with the temperature. On this basis we investigate in detail the scattering mechanisms, in order to account for the mobility limitation in the low-temperature range (T < 10 K). In this case too the role of interface states is found to be crucial. All the calculations are performed within the generalized variational subband wavefunction model. References: 26