Properties of sputtered mercury telluride contacts on p-type cadmium telluride

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Abstract
Because of the high value of its work function (qΦm ∼ 5.9 eV), the semimetallic compound HgTe has been used to realize ohmic contacts of low specific resistance ρc (Ω cm2) on the II-VI semiconductor compound p-type CdTe, in the bulk resistivity range 70 Ω cm < ρB < 45 kΩ cm. The HgTe films were deposited by cathodic sputtering in a mercury vapour, at about 150 °C. Planar contacts were carried out and their specific resistance determined from the Transmission Line Model (TLM) and the Extended Transmission Line Model (ETLM). The methodology of the measurement is developed. For high values of the bulk resistivity (ρB = 1.45 kΩ cm ; 13 kΩ cm ; 16 kΩ cm ; 45 kΩ cm), the ratio ρc/ρB is about 10 -2 cm, and the J(V) characteristics show a quasi linear shape. For ρB = 70 Ω cm, ρc/ρ B is about 10-1 cm, and the J(V ) characteristics are no more linear. The sputter etching of the CdTe surface before HgTe deposition does not affect these results. The chemical nature and/or the structural disorder of the CdTe surface account for the observed deviations to the thermo-ionic effect theory

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