Effect of surface preparation on Ge overlayer growth on (HgCd)Te

Abstract

The interactions between thin Ge overlayers and both cleaved and ion-sputtered Hg1−xCdxTe surfaces have been examined using synchrotron radiation. Ge forms an unreactive layer on cleaved substrates of x=0.21 and x=0.28 with only a small loss of Hg (∼20%) from the interface. In contrast, deposition of Ge onto sputtered substrates results in approximately two (x=0.21 material) or three (x=0.28 material) times the Hg loss relative to the clean surface. The difference in behavior of the sputtered and cleaved material is due to sputter-induced defects at the surface. The increased loss of Hg from the sputtered x=0.28 material is a result of a greater number of these defects caused by the weaker Hg–Te bonding and the corresponding increase in the preferential sputtering of Hg from the surface. No difference was observed between sputtered p-type and n-type material. These results are a consequence of GeTe and HgTe having very similar heats of formation; as such, deposition of Ge provides an indication of the reactivity of (HgCd)Te surfaces.