Physics of photon-flux measurements with silicon photodiodes

A model of the quantum efficiency of a planar silicon photodiode that is useful in connection with high-accuracy optical-radiation measurements is developed. The model is based mostly on macroscopic (phenomenological) optical and electronic properties of the device that must be determined from experiments on the device, but the connection with the microscopic physical properties (band structure) of silicon is made. The predictions of this model differ significantly from recent experimental results for the variation of the internal quantum efficiency with angle for a silicon photodiode as reported by Durnin et al. [ J. Opt. Soc. Am.71, 115 ( 1981)]. A repetition of these measurements is described. The results do not agree with those reported by Durnin et al. but do agree well with the predictions of the quantum-efficiency model.