POSITRON-ANNIHILATION STUDY OF VACANCY DEFECTS IN INAS

Positron Lifetime measurements on InAs wafers have shown that the posi tron bulk lifetime in InAs is 246+/-2 ps. Most samples exhibit a defec t lifetime of 287+/-6.ps, which is attributable to monovacancy-impurit y complexes with a concentration of 7+/-2x10(16) cm(-3). Very heavily doped n-type samples exhibit a defect lifetime of 332-340 ps. The defe cts in these samples have divacancy character, but change their config uration at low temperatures to a monovacancy-type defect. The concentr ation of these defects is also close to 10(17) cm(-3). Both types of d efects are stable for rapid thermal annealing up to 850 degrees C, and both defects are neutral. It is proposed that the formation of the di vacancy-type defects may be correlated with a discrepancy between the carrier concentration and the total dopant concentration.