Properties Of rf Triode-Sputtered (Hg1-xCdx)Te Thin Films

The advantages of r.f. triode sputtering in a Hg atmosphere for deposition of (Hgl-xCdx)Te thin films for low-cost photoconductor and ohotovoltatic infrared detector arrays on electronically-active Si substrates are discussed. It is shown by optical absorp-tion data that the composition of films can be changed from x = 0.1 to 0.27 by changing the relative percentages of HgTe and CdTe particles in sputtering targets, made by cold-pressing a homogenized mixture of these particles. Changes in the physical topography and composition of the surface of pressed-powder targets when bombarded with Hg are described. The mobility and implied carrier concentrations at 24 and -188°C of n and p-type films with different compositions in the 0.18 < x <0.27 range were measured by the Van der Pauw technique. The films were deposited under different sputtering conditions onto high resistivity CdTe and Si substrates with (111) surface orientation. The film properties were improved by post-deposition annealing in a Hg atmosphere using a two-zone furnace. An increase in electron mobility of n-type films to values up to 17 and 50 percent of those for bulk material at -188 and 24°C respectively were obtained using unoptimized annealing parameters.