MOS technology development on 150 mm Ge wafers

Abstract

High purity crystalline germanium has several applications in optoelectronic devices. These include as a substrate and active component of tandem, high efficiency solar cells used in concentrator and space photovoltaics. Here, we are looking at the development of a Ge-based charge coupled devices (CCD) to be used in conjunction with large, terrestrial telescopes used for astronomical studies of red shifts in galaxies and other celestial bodies. In one photovoltaic phtotvoltaic application, large bulk recombination lifetimes are significant for efficiency improvement when a p-n junction is incorporated into the substrate of a tandem device. In the CCD device, the bulk lifetime is critical for low dark current. Also, the development of an insulating gate technology, with low interface recombination velocity, is a critical component of CCD development. Here we used transient photoconductive decay as a metric to evaluate the performance of such interfaces. Bulk lifetimes exceeding 2 ms were found in some high purity materials. The effects on the lifetimes after annealing of the Ge at 300C and 600C was studied. The results of various processing experiments and protocols will be reviewed.