Electrical characterization of p-type ZnSe:Li epilayers grown on p+-GaAs by molecular-beam epitaxy

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Abstract
Small‐signal ac admittance data are presented, and shown to provide accurate and unambiguous evidence of p‐type behavior in Li‐doped ZnSe epilayers grown on p+‐GaAs. The devices measured are two‐terminal vertical‐transport structures, with unequal‐area contacts in order to distinguish effects arising from the top metal Schottky barrier from those arising from the heterojunction. Qualitative features of the data alone are sufficient to determine the (positive) sign of the mobile carriers in the ZnSe. The data are analyzed using an equivalent‐circuit model shown to be reliable for n‐type ZnSe, from which the net doping and the ZnSe resistivity are extracted. Using these quantities, the ZnSe hole mobility is found to be about 28±4 cm2/V s. Schottky barrier and heterojunction barrier heights are also determined.