Characterisation of reactive ion etching induced type conversion in HgCdTe

Magnetic field dependent differential Hall effect and resistivity measurements have been used to study the transport properties of Au-doped Hg_0.77Cd_0.23Te which had undergone p to n type conversion by reactive ion etching. Analysing the data by quantitative mobility spectrum analysis shows that after two minutes of etching in a CH₄/H₂ plasma at 0.4 W cm^-2 RF power density, the 17 μm thick H_0.77Cd_0.23Te epilayer had been totally converted from p- to n-type down to the substrate. This is in stark contrast to results on Hg_0.69Cd_0.31Te which indicate a conversion depth of 2-3 μm. The analysis indicates the presence of two electron species with peak conductivity at 2.3×10⁵ cm 2 V^-1 s^-1 and 9.3×10⁴ cm² V^-1 s^-1 respectively. A depth profile of these two carriers is also presented.