Formation of thermal defects in silicon grown by means of float zone melting

The factors of formation of thermal donors (TDs) and thermal acceptors (TAs) silicon with a low oxygen concentration grown by means of float-zone melting are discussed. The results of thermal treatment in a temperature range of 400-1150 degrees C show that interstitial iron atoms produce the largest contribution to formation of TDs. Substitutional atoms of iron are probable drivers of TA formation in the process of hightemperature treatment (HTT). Iron precipitates formed during low-temperature annealing (400-600 degrees C) also contribute to TA formation. The TD and TA densities after HTT depend on the type and the density of structural defects in the material and the conditions of thermal treatment: the cooling rate and the gas medium (oxygen or argon).