The formation of stable ohmic contacts to MBE grown CdTe layers

The properties of Al contacts to n-type CdTe epilayers have been compared w ith those for In contacts with a view to establishing a contacting technolo gy suitable for the fabrication of stable low resistance junctions to CdTe layers and multilayer devices. It has been confirmed that, as for bulk grow n n-CdTe, ohmic contacts can be formed using vacuum evaporated In but the r esultant devices are unstable due to the rapid inward diffusion of In. For the case of Al contacts, simple evaporation does not yield ohmic behaviour. However, stable ohmic Al-CdTe junctions are found to be achieved making us e of an ion-assisted plating technique in which the semiconductor surface i s exposed to an inert gas discharge prior to and during the early stages of the Al vapour deposition process. This result is attributed to the removal of surface contamination prior to metal deposition, allowing an intimate m etal-semiconductor interface to be produced. (C) 2000 Elsevier Science Ltd. All rights reserved.