Thermostimulated Photoconductivity Method. Application to GaAs

A new simple method to reveal deep levels in photosensitive crystals is proposed and demonstrated using a group of samples of SI GaAs. The method is based on ac photoconductivity measurements during linear change of temperature, when the quasi-Fermi level crosses the impurity and defect levels present in the band gap. More than 10 maxima are observed in the temperature region 6 to 300 K for lambda-exc = 1.03-mu-m. Results obtained with samples of different producers document the diagnostic potential of this method. Background theory is presented together with numerical simulation to demonstrate its basic features. Dependence of the results on excitation density, applied potential, heating rate, chopping frequency, and excitation photon energy is checked and discussed together with a comparison with transient spectroscopies and TSC method.