MICROSCOPIC NATURE OF THERMALLY STIMULATED CURRENT AND ELECTRICAL COMPENSATION IN SEMIINSULATING GAAS

In this work undoped semi-insulating (SI) GaAs grown by vertical gradi ent freeze and liquid encapsulated Czochralski methods was studied by near-infrared absorption (NIRA), thermally stimulated current (TSC) an d positron annihilation techniques. The positron experiments reveal bo th gallium and arsenic vacancies, as well as gallium and arsenic antis ites, in the samples. By comparing the results from the TSC and positr on measurements, the following relations are found in the defect conce ntrations: trap T-2 correlates with the arsenic antisite and trap T-5 with the arsenic vacancy. The ionized fraction of the arsenic-antisite -related EL2 defect is obtained from NIRA measurements. The positive c harge of these ionized EL2 defects correlates with the net negative ch arge, 3[V-Ga(3-)]+2[Ga-As(2-)]-[V-As(+)], related to the gallium vacan cies and antisites and arsenic vacancies detected in positron measurem ents. The intrinsic defects may thus contribute significantly to the e lectrical compensation in SI GaAs. (C) 1997 American Institute of Phys ics.