ABSTRACT
A new technique for evaluating the electrical properties of semiconductor wafers and devices using laser-generated Photo-Charge Voltage(PV) measurements is presented. The technique is based on the measurement of the change in the surface electrical charge induced by a modulated laser beam. This charge is measured capacitativly as a voltage, whose amplitude depends on the surface properties of the sample. In Photocharge Voltage Spectroscopy measurements, the sample is illuminated by both a steady state monochromatic bias light and a pulsed laser. The monochromatic light is used to create a variation in the steady state population of trap levels in the space charge region which does result in a change in the measured voltage. A qualitative analysis of the proposed measurement is presented here along with experimental results performed on GaAs samples passivated with a thin ZnSe film of variable thicknesses. The decrease in surface recombination velocity of GaAs samples as a function of the thickness was measured until a critical thickness is reached.
