Terahertz Plasma Annealing of Gallium Arsenide in a Microcavity Resonator Powered by a Gyrotron

The combination of low specific intrinsic conductivity and nanosecond relaxation time of photoconductivity allows us to consider gallium arsenide (or GaAs) to be the most promising semiconductor in the terahertz frequency range. The known design of a nanosecond waveguide semiconductor switch contains a microcavity that makes it possible to achieve air-breakdown field values of ~25...30 kV/cm at a 400-millisecond pulse power of about 90 W from a gyrotron with a frequency of about 270 GHz. Extreme power densities of the order of 200 kW/mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are safely created in a compact volume. A short-term appearance of plasma in the resonator is observed, leading to both an increase in its quality factor at low energies and a decrease in the quality factor at high energies. The change in quality factor is associated with effective cleaning or contamination of the surface of gallium arsenide by chemical elements in the air. There is an optimal irradiation regime that allows for effective, simple and relatively long-term annealing of gallium arsenide from the oxide layer, even without vacuum and additional chemicals. It is expected that the efficiency of semiconductor purification when using vacuum will increase, even to the point of replacing previously known methods.