Fabrication of improved sige alloys for an 18-couple module test

Abstract

N-and p-type Sio.78Geo.22 alloys were fabricated to determine if recently reported improvements in the figure-ofmerit, Z, could be realized in devices. These will be tested in an 18-couple module to directly compare the performance of these materials with that of standard coarse-grain SiGe used in flight programs. We describe the synthesis by vacuum casting and hot pressing p-type SiGe and mechanical alloying and hot-isostatic pressing n-type SiGe. Improved materials and standard materials are characterized and compared. The integrated average figures-ofmerit (573-1273 K) of the improved materials were Z^ = 0.59x10-3 K'^ and Z^ =0.85x10-3 K-^ compared with Z^"^ = 0.52x10-3 K-^ and Z;;" = 0.76x10-3 K-^ for the standard materials. We also report the power factors for improved and standard materials removed from fabricated devices to gain insight as to how subsequent processing impacts performance.