Laser beam interference effects on the photovoltage of a p-n junction diode

A new method for measuring the diffusion length of minority carriers within the plane of a p-n junction diode is described. It is based on the measurements of the photovoltage between the p- and n-layers, when the diode is illuminated by an interference pattern through a window between contacts 1 and 2 on the top surface of the diode. The advantage is that the voltage between a top contact and a bottom contact is independent of the possible differences in the characteristics of the two ohmic contacts on the top of the sample.