Surface and bulk structural defects in Hg1−xCdxTe

Abstract
The techniques of optical microscopy and transmission electron microscopy (TEM) have been used to study the structural characteristics of a surface of a solid state recrystallized Hg1−xCdxTe crystal (x=0.35) cleaved at room temperature. Such surfaces are of special interest because of their wide use in photoemission spectroscopy studies. HgCdTe cleaved surfaces were found to be much rougher than similar surfaces of GaAs crystals, containing numerous steps and regions where fracture was clearly ductile rather than brittle. TEM observations indicate that a step is associated with numerous dislocations where the crack presumably arrested prior to changing direction, implying that the room temperature cleaved surface has a high defect density compared to the bulk crystal. TEM has also been used to characterize the defects associated with etch pits developed using ‘‘Polisar etch 2’’ on the (111)A face of a Hg1−xCdxTe crystal grown by the solid state recrystallization process. While in some cases dislocations were found, a much higher proportion of etch pits were observed to be associated with precipitates, believed to be Te. In general, these precipitates were isolated, although occasionally they were associated with a dislocation line. The form of the precipitates, along with the distribution of the etch pits, suggests that the final defect structure is strongly influenced by the casting stage.