HVEM investigations of crystal defects in S-doped LEC-GaP crystals

Abstract

Crystal defects in GaP crystals produced by the liquid-encapsulated-Czochralski (LEC) method were studied by etch-pit observations and by high-voltage electron microscopy. Three types of etch pits originating from precipitates, long dislocation lines and dislocation loops were distinguished. By TEM observations both coherent and incoherent precipitates, long dislocation lines, Frank loops accompanying stacking faults of intrinsic type and polygonal dislocation loops were found. The polygonal loops formed by straight dislocation lines along crystallographic directions were determined to be interstitial-type edge-dislocation loops on {110} planes having a Burgers sector of α/2〈110〉. The formation mechanism of the polygonal loops and the correspondence between etch pits and TEM images are discussed.