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We report on an investigation of the growth mechanisms of HgTe using a combination of reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The experiments were carried out on untilted (001) CdTe substrates. Growth rates were determined from RHEED intensity oscillations of the (00) specular spot reflection. The amplitude of these oscillations decrease with increasing substrate temperature. Above 178 °C no RHEED oscillations could be measured. Upon reducing the sample temperature below 178 °C these oscillations could again be observed. This cyclic behavior could be induced several times for each sample, indicating a reversible change in the growth mechanism. In order to correlate the surface structure with RHEED observations, several samples have been investigated with STM. Thus, it could be confirmed that a temperature dependent transition occurs during the MBE growth of HgTe from the island growth mode below the critical temperature of 178 °C to a step flow mode above this temperature.

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The formation of ohmic contacts between indium tin oxide (ITO) and MBE-grown n-ZnSe layers has been investigated using x-ray photoelectron spectroscopy (XPS) and currrent voltage (I -V ) techniques. In contrast to metal-ZnSe contacts, ohmic behaviour is found for ITO contacts made in situ to as-grown n-ZnSe layers as well as contacts made ex situ to oxidized layers. It is possible to form ohmic contacts for ZnSe doping levels in the range of n = 2 × 10 17 to 8 × 10 18 cm −3 with contact resistances as low as R c = 9 × 10 −3 cm 2 . By probing the ITO/ZnSe interface with XPS a mechanism for the contact formation is proposed.