TRANSMISSION ELECTRON-MICROSCOPY INVESTIGATION OF EXTENDED DEFECTS INHEAVILY SE-DOPED BULK GASB

Similar to heavy Te-doped (111) Czochralski-grown GaSb, extended defec ts can be found in Se-doped material using high-voltage transmission e lectron microscopy. The defects occur on a large scale even at a low S e level of 2 x 10(18) cm(-3). Significant differences exist between th e defect patterns situated in the core and non-core regions of the cry stal. Ordinary as well as multiple planar defects (Frank loops) and ex tended perfect loops are observed in the non-core area. Frequently, th e multiple stacking faults are partially unfaulted and the unfaulting reaction was analysed. All defects are extrinsic (interstitial) in nat ure. In the core region, by contrast, tangled clusters of perfect disl ocations are predominant. The defect morphology is a result of large-s cale climb processes due to high point defect supersaturation. It is a ssumed that these differences are caused by varying Se content and var iation in crystal stoichiometry (core effect). These result in a highe r surplus of Sb-i interstitials which, in turn, cause an increased cli mb rate in the core region.