Hot-electron emission from silicon into silicon dioxide

Abstract

Recent progress in the study of hot-electron emission from silicon into silicon dioxide is discussed. Experimental techniques include avalanche injection using gated diodes and MOS capacitors, nonavalanche injection using IGFET structures with an underlying supply p - n junction, and optically induced injection using silicon-gate IGFET structures. IGFET structures allow the fields in the SiO2 layer and in the silicon depletion region to be varied independently. In addition, IGFET structures of reentrant geometry allow absolute emission probabilities of the hot electrons to be determined. Such absolute emission characteristics are useful not only for designing silicon devices but also for quantitative testing of theoretical models of the emission process. Several mechanisms of importance in the emission process have been identified. These are the Schottky lowering of the emission barrier, the scattering of hot electrons in the image-force potential well in the SiO2 layer, the tunneling of hot electrons, and the effect of lattice temperature on electron heating. There is also experimental evidence of the dependence of the hot-electron distribution on electric field gradient. At present, only phenomenological models based on the lucky-electron concept have been developed to the point where quantitative comparison with experimental results is possible. The essential features of these models are discussed.