The effect of an interfacial layer on minority carrier injection in forward-biased silicon Schottky diodes

Abstract

It is shown that the degree of minority carrier injection in Au-Si junctions can be substantially increased by the inclusion of a thin interfacial layer between the metal and the semiconductor. When a forward voltage is applied to the junction, a part of this voltage is developed across the interfacial layer. This favours the reduction of the barrier height to minority carriers, which tunnel from the metal into the semiconductor. The minority carrier injection current increases at the expense of the majority carrier current. For a given oxide thickness, γ(= J minority/ J tot) increases with forward bias, approaching a saturation value for a few volts applied to the junction. For a given voltage, γ also shows a variation with interfacial layer thickness, δ, and the present results indicate that an oxide thickness can be chosen to optimise γ. In the case of a gold-silicon junction with an insulating layer of thermally-grown oxide, as δ is increased to 40 Å, the saturation value of γ increased from 10 −4 for δ = 10 A ̊ through a maximum of 2 × 10 −1 for δ ⋍ 30 Å. For oxides prepared by r.f. sputtering, the maximum value of γ is 10 −1 and occurs for δ ⋍ 80 Å. These results are of considerable importance in the improvement of injection luminescence in metal-semiconductor diodes.