Cd-based ohmic contact materials to p-ZnSe

Abstract

In order to explore a possibility to prepare low resistance Ohmic contacts by the conventional deposition and annealing (DA) technique, the effects of ZnSe surface cleaning and formation of an intermediate heterostructure on the electrical properties at the metal/semiconductor interface have been investigated for N-doped p-ZnSe substrates grown by the molecular beam epitaxy (MBE) technique. The turn-on voltage (VT) (corresponding to the breakdown voltage) was significantly reduced by cleaning the ZnSe surface in a saturated bromine water (SBW) solution, which was found to be due to removal of the native oxide layer grown on the ZnSe surface. The addition of a small amount of Cd to the W contact reduced the VT values of the W contacts from about 11 to 6 V. A microstructural analysis indicated the formation of CdxZn1 − xSe layers at the metalZnSe interface with a Cd composition (x) larger than 0.9. From the present experiment, it was concluded that formation of thin large-area CdxZn1 − xSe layers is crucial to reduce the VT value to nearly zero by the conventional DA technique.