Ex situ formation of HgSe electrical contacts to p-ZnSe

Abstract

A novel method of forming semimetal HgSe electrical contacts to p‐type ZnSe through an ex situ growth process has been developed. The ex situ process consisted of deposition of an amorphous Se capping layer on p‐ZnSe prior to removal from the molecular beam epitaxy (MBE) growth chamber. This capping layer protected the p‐ZnSe from contamination and oxidation upon removal from the MBE growth chamber. This capping layer was reacted with Hg to form HgSe by heating to 150 °C for ∼15 min in Hg vapor. Transmission electron microscopy and x‐ray diffraction data showed that the cubic HgSe phase was formed. Auger sputter depth profiling data were consistent with the formation of stoichiometric HgSe. The electrical characteristics of the contacts were studied using temperature dependent I–V measurements which showed that thermionic emission dominated conduction across the interface for low reverse biases (VR<2.5 V). However, thermionic field emission dominated conduction for VR≳2.5 V. The barrier height for thermionic emission and the energy parameter for tunneling were determined to be ∼0.55 and 0.0076 eV, respectively, consistent with an unpinned Fermi level.