Electrical and optical investigation on doping of II-VI compounds using radioactive isotopes

Using radioactive isotopes of shallow dopants (Ag, As, Rb) as well as of na tive or isoelectronic elements (Se, Te, Cd, Sr) which were incorporated as host atoms and then transmuted into relevant dopants (transmutation doping) we investigated doping phenomena occurring in the wide band gap II-VI comp ounds CdTe, ZnTe, ZnSe and SrS by the classical methods of semiconductor ph ysics: Hall effect, C-V and photoluminescence measurements. Thus, we could assign unambiguously defect features in electrical and photoluminescence me asurements to extrinsic dopants by means of the half lives of radioactive d ecay. In As doped ZnSe samples we observed two states: a metastable effecti ve mass like state and a deep state. The occurrence of the latter state is always linked with the high resistivity of As doped ZnSe crystals. The tran smutation doping experiments reveal that the so-called self-compensation ty pical for wide band gab II-VI compounds can be overcome when the thermal tr eatment for dopant incorporation is time separated from its electrical acti vation, achieved using transmutation at room temperature. Under these condi tions we found an almost one-to-one doping efficiency relative to the impla nted dose. Thus, these investigations are a contribution to understanding c ompensation phenomena occurring due to interactions between dopants and nat ive defects during conventional doping treatments.