A manifestation of the tunneling conductivity of a thin-gate insulator in the generation kinetics of minority carriers in metal-insulator-semiconductor structures

Abstract

The kinetics of the minority-charge-carrier generation current I(t), in the Al-n ⁺-Si-SiO₂-n-Si structures with a tunnel-transparent oxide layer, are found to be anomalous. Under depleting gate potentials (V _g<0), sharp peaks are observed in the I(t) curves, whose descending branches attain a steady-state current level rapidly increasing with |V _g|. The observed features are related to the tunneling conductivity of a thin (100 Å) oxide layer and with the impact generation of electron-hole pairs in a space charge region of Si by hot electrons that tunnel into the space charge region. Using this concept, an algorithm of the quantitative description of the experimental data is developed. This algorithm makes it possible to separate the components related to thermal and impact generation and the tunneling current component from the total current I(t). The impact ionization factor (α=1.2±0.2) and the energy of hot electrons in Si space charge region (E _im=4.23 eV) are determined. Dynamic and steady-state current-voltage characteristics for the oxide layer coincide and obey the Fowler-Nordheim law. The position of the current maximum is controlled by external factors that stimulate the generation of non-equilibrium charge carriers; this effect can be used for the development of integrating and threshold sensors.