From Bulk to Nanoscale: Profiling Charge Carrier Mobility in Home-Grown High-Purity Germanium Crystals

Understanding the evolution of charge carrier mobility with dimensional scaling is critical for optimizing the performance of germanium-based devices across a wide range of applications, from radiation detection to next-generation nanoelectronics and quantum technologies. In this study, we present a comprehensive investigation of room-temperature charge carrier mobility in high-purity germanium (HPGe) crystals grown in-house at the University of South Dakota. Both p-type and n-type samples are examined, starting from bulk geometries (1 cm × 1 cm × 200 μm) and progressively reduced in thickness toward the nanoscale regime.

Each sample is mounted on PTFE substrates and processed using optimized surface treatment protocols—including precision bonding and chemical etching—to ensure minimal surface contamination and structural defects. We systematically measure mobility as a function of thickness to capture the crossover from bulk-dominated transport to regimes increasingly influenced by surface scattering, interface states, and confinement effects.

Our results reveal key trends in carrier transport at reduced dimensions and provide insights into the fundamental mechanisms that limit mobility in miniaturized devices. These findings have direct implications for the design and fabrication of ultra-low-threshold detectors, scalable quantum devices, and high-performance Ge-based nanoelectronic components. This work establishes a critical experimental foundation for advancing HPGe technologies in both classical and quantum applications.