Effect of Evaporated Dielectric Materials on the Surface of High Purity Germanium

The effect of evaporated ielectrics on real Ge surfaces has been investi-gated at 80 ~ Using high pur i ty Ge (!ND-- NAI < 1011 cm-8) , insulated gate field transistors (MISFET) were made and coated with an evaporated ielec-tric layer. The number of surface states and the density of states per unit energy have been deduced from the forward transconductance. It has been found that some dielectrics introduce a large number of surface states near the center of the bandgap. The protection of the surface of the active volume of germanium detectors for infrared light,-/-radiation, or particles is a problem which differs in many respects from the surface passivation problem in the silicon transistor or integrated circuit technology. The solu-tions developed for the latter canot be applied to these Ge devices for a var iety of reasons. The main one i