SHALLOW THERMAL DONOR DEFECTS IN SILICON

An ab initio local density functional cluster program, AIMPRO, is used to examine nitrogen related shallow thermal donor defects in silicon. We find the bonding of oxygen with interstitial nitrogen in N-i-O-2i to be almost ''normal,'' but the O atoms move slightly out of their bo nd centered sites causing the deep donor level of N-i to become shallo w. The defect has properties consistent with those experimentally obse rved for shallow thermal donors. We also find that a CiH-O-2i defect h as very similar electronic properties, and suggest that shallow therma l donors do not have a unique composition.