Ion implantation and ion milling in MBE Hg1−xCdxTe films

Direct comparison of the effects of ion implantation with energy E = 20–150 keV (B+ ions) and ion milling (E = 0.5 keV, Ar+ ions) on p-type HgCdTe (MCT) molecular-beam epitaxy-grown films with and without graded band-gap surface layers was performed. Both treatments were found resulting in formation of multi-layer n+–p or n+–n–p structures, comprising a radiation-damaged n+-layer with high electron concentration and, optionally, a deeper n-layer with low electron concentration. Basic processes, which occur in MCT under implantation and milling appear to be similar, and include formation of primary radiation defects, their interaction, and in-diffusion of interstitial mercury atoms with their interaction with defects already present in the crystal. The difference in energy and fluence typically used for ion implantation and ion milling in MCT results in different mechanisms of the formation of the n+- and n-layers. The presence of the graded band-gap surface layer was found to affect the thickness of the n-layer via internal electric field associated with the energy gap gradient.