A deep-level transient-conductance spectrometer for high-resistivity semiconductors, using a radiofrequency (approximately 40 MHz) marginal oscillator as a conductance detector, is described. Spectra are generated by periodically filling deep-level trapping centres with carriers stimulated by a pulsed GaAs laser, and processing the trap-emptying conductance signal through an exponential Miller correlator as the sample temperature is slowly ramped. Simple capacitive coupling of samples to the oscillator tank circuit eliminates problems such as unwanted defect annealing and other material changes often associated with the high-temperature techniques necessary for ohmic contact formation. Representative deep-level spectra are given for semi-insulating Bridgman-grown CdTe.
- DEEP LEVELS
- OPTICAL TRANSIENT-CONDUCTION SPECTROSCOPY