Rectifying Schottky Contact in ZrN/Polycrystalline p-Ge

Fermi-level pinning (FLP) at the metal/Ge interface makes it difficult to control the Schottky barrier height, which forces an ohmic behavior on p-Ge and a rectifying behavior on n-Ge. This study first demonstrates the rectifying behavior on polycrystalline (poly) p-Ge on a glass substrate, using sputter-deposited ZrN contacts under 350 °C process. The rectifying characteristics depend on the poly-Ge quality derived from the grain size and the defect-induced acceptor density. The highest quality Ge is formed by solid-phase crystallization (SPC) of amorphous Ge deposited at 125 °C and exhibits the lowest reverse leakage current as well as the highest hole (the lowest electron) barrier comparable to a single-crystal Ge substrate. In contrast, the Zr contact exhibits ohmic behavior, suggesting the importance of ZrN in alleviating FLP. The forward and reverse currents are determined by Ge resistance and grain boundaries in Ge, respectively. These technologies will further aid the development of electronic devices on glass or plastic substrates with low heat resistance, including n-channel thin-film transistors.