Deep level spectroscopy in semiconductors using transient surface photovoltage

A contactless method to evaluate deep impurity and defect levels is described. This method was tested in p-type silicon. The method was based on the use of a transient surface photovoltage signal that was generated when a semiconductor was illuminated with short pulses of radiation of energies greater than the band-gap. The photovoltage transients were recorded and analyzed as the temperature cycled between 80 and 400 K. Since the generation of electron-hole pairs gives rise to a lowering of the energy barrier at the surface of the semiconductor, this signal can therefore be enhanced or quenched by applying the appropriate DC-bias voltage. A simplified analysis of these transients is presented. This simple technique can be extended to study deep levels in p-n junctions and Schottky-barrier diodes