The metallic conductivity of exciton liquid is discussed. With increasing of exciton density in many-exciton systems there are two important transitions. They are the gas-liquid and the insulator-metal transitions. The gas-liquid transition, which is the first order phase transition is usually accompanied by the insulator-metal transition. In the case of multivalley semiconductors the electron-hole liquid phase is always a metallic one. Modified Mott criterion for multivalley case is given. In one valley semiconductors with spherical effective masses of both electrons and holes the existence of insulating e-h liquid is possible at least theoretically.

A quasiclassical model of an Auger transistor based on a MIS structure with a tunnel-transparent oxide layer (Al-SiO2-n-Si) is constructed. The transistor has a double-layer emitter and a quantum-well base induced by an electric field. The injected electrons receive a substantial part of their energy (up to 0.7 eV) from heating during their passage above the self-consistent hole quantum well at the silicon surface. The impact ionization threshold can thus be obtained at a lower potential drop across the oxide. The depth of the quantum well is calculated in the Hartree approximation with allowance for the exchange and correlation corrections. The electron and hole tunneling currents are calculated in a quasiclassical approximation. The current-voltage characteristics of the Auger transition are calculated on the basis of a plot of the impact ionization coefficient versus the electron energy. The theoretical I-V characteristics of the Auger transistor are in good agreement with the experimental data.

The results of an experimental study of the static characteristics of a silicon Auger transistor with a tunnel metal-oxide-semiconductor (MOS) emitter and an induced base are presented. A tunnel-thin oxide in the MOS emitter was formed in 20-60 min by oxidation in dry oxygen at T=700-degrees-C. The emitter dimensions are 20 X 20 mum. The dependence of the differential gain beta(d) on the emitter-base voltage has regions of a steep rise spaced at intervals corresponding to an increase in the energy of the tunneling electrons by a value on the order of E(g) of silicon; these intervals correspond to a rapid slowing down of the rise of the base current I(B), indicating the appearance of an internal source of holes. This behavior suggests that a multistage Auger ionization can be produced by the tunneling hot electrons in the space charge region of the collector. The transistor gain is beta(d)=700-900, which can be easily reproduced. This reproducibility, together with the expected faster response, make these transistors promising for use as possible silicon microelectronic components.