Conversion of conductivity type in Cu-doped Hg_0.8Cd_0.2Te crystals under ion beam milling

The behaviour of copper dopant in p-Hg1−xCdxTe single crystals is analysed for in-diffusion in the samples with heterogeneous distribution of Hg vacancies and for ion beam milling. For the case of low Hg vacancy, p-Hg1−xCdxTe (x ∼ 0.2) material, copper is found to diffuse by a relay-race interstitial mechanism at low temperature. When the Cu-doped p-Hg1−xCdxTe samples are exposed to ion milling, the p–n conversion of conductivity type occurs in a substantially thick subsurface layer (∼10 µm). Unstable donor centres such as copper in interstitials rapidly relax so that residual donors control the conductivity in a converted layer after several hours. The possible causes of the incomplete p-type reconversion are discussed.