A study of void defects in metalorganic molecular-beam epitaxy grown HgCdTe

Abstract

Void defects that occur under Hg deficient conditions during the metalorganic molecular beam epitaxy (MOMBE) growth of HgCdTe have been characterized using secondary electron microscopy (SEM) and energy dispersion spectrometry (EDS) mapping as well as by EDS quantitative analysis. For a set of HgCdTe samples grown under a range of Hg fluxes, it was found that the surface morphology had a significant dependence on the Hg flux. An optimum growth window defined by a narrow range of Hg fluxes was identified in which there exists a smooth surface with few voids, whereas at either side of the Hg window surfaces were rough. This surface morphology correlated very well with a minimum in the x-ray line widths and maximum hole concentration and mobility values. This correlation is important for the growth of HgCdTe materials and subsequent device fabrication. Several types of void morphologies have been observed with different correlation to Te and Hg. It was found that there is a pronounced Te enrichment and Hg deficiency associated with most of the developed voids, as compared to the composition of the HgCdTe films. It was also found that most of the voids originated within the HgCdTe film. A mechanism for void formation and growth is proposed. In addition, it was found that annealing caused the voids to separate from the HgCdTe film.