Effect of surface preparation on contact properties to high resistivity Cd1-xMnxTe:In

• Surface Preparation Influences I–V Characteristics in CMT crystals. • Air-exposed or Passivated vs. Bromine Etched Surfaces. • A Comparative Study of Contact Performance. • Bromine Penetration Depth Depends on Crystal Termination: Cd vs. Te Sides. Cd 1−x Mn x Te (CMT) is a promising material for X-ray and gamma-ray detection, where high-resistivity crystals and stable, low-leakage electrical contacts are essential. This study focuses on indium-doped CMT crystals grown using the low-pressure Bridgman method. Electrical contacts were applied by directly sputtering an AuPd alloy onto crystal surfaces prepared using different methods, including etching the samples in varying concentrations of bromine-methanol solutions or aging them in the air. Cd- and Te-terminated surfaces of (111)-oriented zinc-blende CMT samples were examined. The influence of surface preparation on contact performance was evaluated using I-V measurements at room temperature. Techniques like XPS, RHEED as a function of temperature, SIMS, SEM, AFM, and XRD were employed to assess surface conditions. XPS revealed significant TeO 2 formation on air-exposed surfaces. SIMS confirmed the presence of a tellurium-rich layer up to 15 nm thick on the Te-terminated surface etched in 0.1 % bromine-methanol solution, known as “epi-ready” etching. The RHEED, AFM, and SEM analyses demonstrated surface reorganization upon vacuum annealing at 85 °C. The critical role of surface treatment in achieving reliable electrical characteristics and surface quality in CMT-based detectors is highlighted. The SIMS analysis demonstrated that “epi-ready” etching leads to bromine penetration into the bulk of the CMT samples.