ALUMINUM-DOPED N-TYPE ZNSTE ALLOY GROWN BY MOLECULAR-BEAM EPITAXY

Successful n-type doping of ZnSTe alloy using elemental aluminum sourc e has been carried out by molecular beam epitaxy. Hall effect measurem ent (300-77 K) was performed on as-grown ZnS0.977Te0.023 epilayers wit h various dopant concentrations. Electron carrier concentration as hig h as 1.3X10(19) cm(-3) has been achieved. For carrier concentration hi gher than 5X10(18) cm(-3), the carrier concentration is independent of temperature, possibly indicating formation of a very shallow donor le vel. A group of ZnS1-xTex epilayers with different x values was doped using a constant aluminum beam flux for studying the dependence of the dopant activation on Te composition. Good activation of Al dopant was obtained for x value from 0 to a few percent, but it became poor for larger x value and finally Al became inactive for x values higher than 10%. Room temperature photoluminescence measurements on doped and und oped ZnS and ZnS1-xTex layers indicate that Al dopants from deep-level radiative centers in addition to a shallow donor level. The character istics of these deep levels as a function of Te composition have also been studied. (C) 1996 American Institute of Physics.