New aspects for investigation of carrier transition through deep levels in GaAs by a piezoelectric photoacoustic technique

The temperature variation of the piezoelectric photoacoustic (PPA) signal intensity of semi-insulating (SI) GaAs from 20 to 150 K was measured. Four distinctive peaks at 50, 70, 110 and 125 K were observed. From the theoretical analysis based on the rate equations of electrons in the conduction band and several deep levels, we concluded that two distinctive peaks at 70 and 125 K were due to the nonradiative recombination of photoexcited electrons from EL2 to EL6⁺ and EL10⁺/EL11⁺ deep levels, respectively. Deep levels with extremely low concentration (10¹²-10¹⁵ cm^-3) were clearly detected in SI-GaAs by using PPA method for the first time.