Electrical and Physicochemical Study of the Metal/p-HgCdTe Interface for MCT-Based Infrared Detectors

Mercury cadmium telluride (MCT) cooled infrared (IR) detectors remain a technological benchmark for the IR community as defined by Rule 7 (J. Electron. Mater. 37:1406). Their performance depends on the ability to resolve small temperature differences between two black bodies, particularly for defense. This thermal resolution is highly sensitive to even slight variations in device quality and is commonly evaluated using residual fixed-pattern noise (RFPN), a second-order performance metric for focal plane array (FPA) characterization. Recent research efforts are focused on developing detectors capable of operating at high operating temperatures (HOT). However, increasing the operating temperature typically leads to a higher number of anomalous pixel responses and elevated dark current and noise, resulting in degradation of detection capabilities. One suspected cause of this degradation is the quality of the metal/ p -type semiconductor interface, particularly due to variations in the Schottky barrier height (SBH). The non-ohmic behavior frequently observed at this interface is commonly attributed to the presence of a Fermi-level pinning effect. This work aims to investigate that hypothesis with a detailed physicochemical analysis of the interface’s formation and composition including a comprehensive correlation with electrical measurements. Metal contacts were fabricated on p -type Hg 0.7 Cd 0.3 Te doped with arsenic, with a doping concentration of approximately 10 18 cm −3 . A consistent surface preparation and deposition method with different metals were applied to form contacts. Electrical properties were characterized using the transfer line method (TLM) at 300 K and 110 K to extract specific contact resistance. To probe the initial surface and buried interface, hard x-ray photoelectron spectroscopy (HAXPES) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed, providing insights into the chemical composition and oxidation phenomena involved in interface state formation. This study highlights the predicted dependence of SBH on the intrinsic nature of metal at 300 K. At low temperature, this dependency is no longer valid due to the predominance of tunneled and trap-assisted conduction. The presence of a buried tellurium oxide layer could explain this deviation, as it may govern the electrical properties of the contact and determine the SBH.