Compensation of CdTe by Doping With Gallium

Abstract

Semi-insulating CdTe single crystals doped with Ga were grown from the vapour phase by the modified Markov technique MMT. The study of the resistivity map in the cross-sections cut a long the growth direction has been performed. The compensation phenomenon is analysed in the framework of the three levels Fermi-statistic model. It is shown that a semi-insulation behaviour throughout the ingot is due to the compensation of shallow impurities by the deep level. From the low -temperature photolum inescence spectra it was concluded that shallow donors (GaCd) are partly compensated by (GaCd-VCd)-and (GaCd-CdTe) complexes and by residual acceptors (NaCd, CuCd) . The microscopic structure of (GaCd-CdTe) complexis proposed based on the value of its local phonon mode and the growth conditions. A native defect like TeCd which has a deep level near the middle-band-gap is suppose to give a stable compensation and a tolerance for variation in shallow impurity concentrations.