Vacuum Deposition of Hg0.8Cd0.2Te

Abstract

Vacuum deposition of Hg_0.8Cd_0.2Te has been studied using both flash evaporation and separate molecular beams of the components. At substrate temperatures near 100°C there is considerable reevaporation of mercury from the growing layer. Consequently, deposition at these temperatures by flash evaporation of Hg_0.8Cd_0.2Te gives layers that consist of Hg_1−xCd_xTe with x>0.2, together with a second phase of unreacted tellurium. This effect imposes restrictions upon the use of flash evaporated layers for the study of composition‐dependent properties. The loss of mercury may be compensated, either by adding a source of mercury to the flash evaporation system, or by using separate molecular beams with the mercury in excess. These techniques were used for growth at temperatures as high us 150°C. The conditions needed for growth of single phase Hg_0.8Cd_0.2Te are in agreement with a simple model for evaporation of mercury from the growing surface. Layers grown in the temperature range 70°–150°C are all n type with extrinsic conduction. This leads to the suggestion that, at low temperatures, Hg_0.8Cd_0.2Te exists stably, only as a Te‐deficient phase.