Electrophysical properties of the germanium MIS-transistor

The characteristics and interface properties of n-channel and p-channel Ge-IGFET´s are investigated. Transistors were fabricated using Ge-SiO2-Si3N4structure. This structure is stable to a thermofield stress and has a low density of interface states (Nss∼10¹²cm^-2eV^-1). The experimental Ge-IGFET characteristics measured at BOOK and 77K are presented and compared with theory. The strong influence of the reverse bias between the channel and the substrate on the effective mobility of carriers in the channel are reported. This effect is due to decreasing of the carrier drift mobility in the channel rather than to the change of the interface states charge. The data of the investigations of Ge-IGFET in weak inversion are presented. The spectrum of interface states Nss(E) is determined. This spectrum is exponential and is approximated by Nss(E) = 10¹²exp[12(E-Eo)] cm^-2eV^-1in energy range 0.17eV < E < 0.3 eV, where Eo= 0.17 eV, and coincides with spectrum obtained from the temperature dependence of the threshold voltage measurements.