Low Resistance Ohmic Contacts to n-Hg1−xCdxTe Using a HgTe Cap Layer

Abstract

AbstractNon-alloyed ohmic contacts of HgTe on Hg1−xCdxTe (x = 0.60) with metallisations of Ti, In and Au have been investigated. Layers of HgTe with thickness in the range from 0.1 μm to 1.0 μm were grown by organometallic epitaxy either as an abrubt or a graded junction, depending on the in-situ annealing conditions. The layer thickness and the extent of interdiffusion with the Hg1−CdxTe were determined using Rutherford backscattering spectrometry (RBS). The results have shown that an abrupt rather than a graded structure was essential in order to achieve the minimum value of specific contact resistance, ρc, of ≈5 × 10−5 Ωcm2. In addition, a critical thickness of HgTe (≥0.2 μm) was required in order to obtain a substantial reduction in ρc. For these metal/HgTe/Hg1−xCdxTe contacts, the metal Ti has produced the lowest values of ρc and greatest adhesion to the HgTe. Both of these properties have been attributed to the strong interfacial reaction of the overlayer of Ti with HgTe.