Upper limit of two-dimensional electron density in enhancement-mode Si/SiGe heterostructure field-effect transistors

摘要

In this paper, we present our study of the maximum electron density, n_(max), accessible via low-temperature transport experiments in enhancement-mode Si/Si_(1-x)Ge_x heterostructure field-effect transistors. Experimentally, we find that n_(max) is much higher than the value obtained from self-consistent Schrodinger-Poisson simulations and that n_(max) can be changed only by changing the Ge concentration in the Si_(1-x)Ge_3 barrier layer, not by varying the barrier layer thickness. The discrepancy between experiments and simulations is explained by a non-thermal-equilibrium tunneling-limited model.