Cryogenic Material and Electrophysical Changes in Si and GaAs

This study presents a comprehensive investigation of the cryogenic electrical and material behavior of silicon (Si) and gallium arsenide (GaAs) over a wide temperature range from 4 to 300 K and doping concentrations spanning intrinsic conditions up to 1×10¹⁸ cm⁻³. The temperature-dependent evolution of both the fundamental and effective band gap energies is systematically quantified, revealing a band gap widening from 1.12 to 1.17 eV in Si and from 1.42 to 1.51 eV in GaAs as the temperature is reduced from room temperature to 4 K. Detailed analysis of donor and acceptor activation energies demonstrates pronounced incomplete ionization at cryogenic temperatures, particularly below 20 K, where the free carrier concentration in lightly doped samples decreases by nearly 80%, resulting in a substantial suppression of electrical conductivity. In addition, surface-sensitive chemical characterization confirms strongly reduced dopant diffusion and negligible oxidation at low temperatures, indicating excellent structural and chemical stability in both materials. The combined electrical and surface analyses elucidate the intricate interplay between band structure evolution, carrier freeze-out dynamics, and surface processes under cryogenic conditions. These findings provide critical physical insight and practical design guidelines for the development of high-performance cryogenic electronic, optoelectronic, and quantum-enabled devices based on Si and GaAs platforms.

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