Selective formation of ohmic contacts to n-GaAs

A new process is presented for ohmic contact realisation to n-GaAs. The process enables selective formation of ohmic contacts showing ohmic characteristics without an alloying process. This is realised through the deposition of a heavily doped n-Ge layer on an n-GaAs layer. It is possible to grow a Ge layer on GaAs without deposition on SiO2 which is used as a mask. A Ge layer with doping in excess of 1019 cm¿3 can be obtined, using GeH4, PH3 and H2 as source gases. This doping level is sufficiently high to exhibit nonalloyed ohmic characteristics.