Ohmic contacts to p-type cadmium telluride and cadmium mercury telluride

Abstract

The different techniques of making ohmic contacts to p-type CdTe are reviewed and discussed. Mercury telluride, whose work-function matches perfectly that of p-type CdTe, is shown to be more favourable than Au or Pt. The HgTe contacts deposited by close spacing isothermal growth present a room temperature specific contact resistance ten times lower than so far reported. Hall effect measurements have been performed down to low temperatures on several undoped p-type CdTe and Cd_0.7Hg_0.3Te crystals. Ionisation energies of 0.05-0.07 and 0.13 eV for CdTe and 0.024 eV for Cd_0.7Hg_0.3Te have been determined and the nature of the responsible centres discussed.