Image force effects on the short wavelength (UV) photoresponse of silicon Schottky barriers

Abstract

An experimental study has been made of the short wavelength λ response of near-ideal silicon Schottky barrier photodetectors. It is shown that the major cause of reduced quantum efficiency (Q.E.) in this range of λ is the collection by the metal of majority carriers photogenerated within the image force maximum, in agreement with the theoretical predictions of Green. The bias-voltage dependence of the photocurrent in the near ultraviolet region is in good quantitative agreement with the image force model, with a Q.E. near unity for large reverse bias decreasing by approx. 15% at zero bias for λ = 0.37 μm, for example. The Q.E. under short-circuit conditions is relatively independent of λ for λ ≳ 0.45 μm, falling rapidly with decreasing λ from 95% at 0.45 μm to approx. 80% at 0.35 μm, again in good quantitative agreement with the above theory.