Percolation problem in boron - Implanted mercury cadmium telluride

We used high-resolution x-ray diffraction to measure precisely structural m odifications in variously composed Hg1-xCdxTe layers which were fabricated by different growth techniques and subjected to boron implantation to form p-n junctions. Analysis of implantation-induced features in the diffraction profiles allowed us to deduce the interstitials concentration remaining in the sample interior and, thus, to obtain important information on post-imp lantation defect migration. As a result, a percolation problem in the migra tion of Cd interstitials was discovered in samples with x < x(c) (x(c) = 0. 265 is the percolation threshold). Due to the percolation problem, the impl anted samples having Cd content below and above x(c) exhibited very differe nt surface recovery, which was visualized by high resolution scanning elect ron microscopy. It was found that additional annealing at 250-300 degrees C stimulates diffusion of formerly locked Cd interstitials and leads to the change in the conductivity type (n-p) at the expense of remaining non-compe nsated vacancies. The percolation problem in samples with x < x(c) seems to be responsible for limited mobility of implanted boron and difficulties in boron activation in Hg1-xCdxTe-based devices for 8-12 mu m atmospheric tra nsparency window.