Mercury Cadmium Telluride Sputtering Research.

Abstract

Abstract : A large number of 5-10 micron thick n and p-type films on Si and CdTe substrates were prepared by Hg vapor rf triode-sputtering using pressed-powder targets. The targets had different percentages of CdTe particles and thus films with the CdTe mole percent (x values) between 0.18 and 0.27 were obtained. It was demonstrated that the grain size and mobility of the sputtered polycrystalline films, with a high degree of (111) crystal orientation, could be greatly increased by annealing the films at 553-623 degrees Kelvin in a Hg atmosphere. For example, x = 0.27 films had as-sputtered electron mobilities less than 20 percent of ideal bulk-crystal material at 300 degree Kelvin and less than 4 percent at 85 degree Kelvin with free electron concentrations 20 times intrinsic material at 85 degrees. After annealing at 553 degrees in 74 mm pressure of Hg, the electron mobilities were 71.5 and 16.5 percent of ideal values at 300 and 85 degrees respectively with carrier concentrations in the 10 to the sixteenth per cubic cm range. Similar results were obtained using CdTe and Si substrates and for other compositions. For films with 0.18 CdTe mole percent, electron mobilities of 24,000 cm squared per volt second were measured at 85 degrees. Two step annealing processes, with separate temperatures for grain size enlargement and stoichiometry adjustment, and low temperature heat treatments for preventing peeling by grading the Si-(Hg,Cd)Te interface appear necessary for further optimization of the annealing effects. (Author)