New type of homointegrated and heterointegrated circuits

Abstract

The use of GeO2 as a stable mask for the selective growth of epitaxial Ge layers through unmasked windows on Ge substrates or on previously deposited Ge layers in GaAs substrates is here described. In both cases, the Ge epitaxial layers have been grown at a relatively low temperature, 330–420 °C, using the GeI2 disproportionation reaction. The surfaces of the oxide and the Ge layers grown in regions surrounded by GeO2 appear to be mirror smooth when observed with a scanning electron microscope up to 11 500× magnification. The oxide-germanium boundary has been found to be free from preferential growth of Ge. New applications of this technique to Ge homointegrated circuits (e.g., Ge layers grown on Ge-or Cr-doped semiinsulating GaAs substrates) and Ge/GaAs heterointegrated circuits are discussed. Also described is the possibility to integrate other materials and new heterojunction devices compatible with Ge and several other devices which are not feasible in Si alone.