RADICAL ASSISTED METALORGANIC CHEMICAL-VAPOR-DEPOSITION OF CDTE ON GAAS AND CARRIER TRANSPORT MECHANISM IN CDTE N-GAAS HETEROJUNCTION/

The growth and carrier transport mechanism in CdTe on the GaAs substra te is reported. Epitaxial layers of CdTe were grown on n- and semi-ins ulating GaAs substrates by the hydrogen radical assisted metalorganic chemical vapor deposition technique at a low pressure. Dimethylcadmium and diethyltelluride were used as the source materials. The growth wa s carried out in the substrate temperature range of 150-300 degrees C. The grown films have high resistivity in the order of 10(7) Omega cm for the entire growth range. Applicability of this heteroepitaxial CdT e layer on n-GaAs as an x-ray detector was then investigated. The carr ier transport mechanism of the CdTe/n-GaAs heterojunction was studied by means of current-voltage measurements at different temperatures. Th e forward current was characterized by multitunneling capture-emission current and space charge limited current. The reverse current was con sidered as the generation current from the heterojunction interface st ates through the analysis of capacitance-voltage measurement. It is fo und that for devices using minority carriers, this heterojunction alon e is not useful because of the high concentration of interface states. A suitable modification, like an isotype heterojunction between GaAs and CdTe before forming the p-n junction, seems to be necessary. (C) 1 998 American Institute of Physics.