Contents I. Introduction
Semi-insulating Gallium arsenide (GaAs), or pure GaAs without doping has become widespread among rapid switching devices [1], [2], [3], [4] in subterahertz bands. The main advantages of GaAs over other semiconductors are: the nanosecond duration of photoconductivity relaxation, the high breakdown threshold, and the low losses in the terahertz bands. Under room conditions in open air, the surface of pure GaAs is covered with a thin native film of oxides and hydroxides [5]. The film is usually harmful for semiconductor devices, as its physics, still being typical for a semiconductor, differs from that of the pure GaAs. The oxide layer generally increases the effective tangent loss, making it much higher than one for a pure medium. There are several methods of treating the film, in particular, thermal annealing [5], [6], chemical dissolving [7], [8], or deoxidation by chemical reactions [9], [10]. All of the known methods have some drawbacks, from lattice defects and unpredictable geometry of the resulting surface to the requirements of vacuum or additional chemicals. In this research, we study the recently discovered phenomenon of enhancement of resonant characteristics in a GaAs-based microscopic resonator cavity under excitation by pulsed powerful subterahertz radiation [11]. The rest of this article is organized as follows. This study covers experimental phenomena of oxide removal using subterahertz radiation in Section II, microscopic investigations of the wafer in the different stages of the experiment in Section III, a simplified theory of thermal distribution within the wafer inside the electro-magnetic resonator cavity in Section IV, and its comparison to the experiment in Section V. Finally, Section VI concludes this article.
