The temperature variation of the piezoelectric photo-thermal signal intensity of semi-insulating material was measured at 20 to 150K. Peaks in the piezoelectric photo-thermal signal were observed at 50, 70, 110 and 125K. From a theoretical analysis which was based upon the rate equations of electrons in the conduction band and deep levels, it was concluded that the observed peaks were due to non-radiative electron transitions through EL6, EL7, EL15, and an unspecified deep level, respectively. Deep levels having extremely low concentrations (1012 to 1015/cm3) could be clearly identified in semi-insulating material by using the piezoelectric photo-thermal method.

Investigation of Deep Levels in Semi-Insulating GaAs by Means of Temperature Change Piezoelectric Photo-Thermal Measurements. A.Fukuyama, A.Memon, K.Sakai, Y.Akashi, T.Ikari: Journal of Applied Physics, 2001, 89[3], 1751-4