GaAs oxidation with Townsend-discharge three-electrode microreactor

Abstract

We have investigated the plasma-chemical anodic oxidation of single-crystal GaAs under the action of products of the non-self-sustained dc Townsend discharge in a 98%Ar + 2%O2 gas mixture. In the experiments, an original design of a plasma-chemical microreactor with two discharge gaps and a plane-parallel arrangement of electrodes is used. In one of the gaps of the device, a self-sustained Townsend discharge is excited. The stability of its spatially uniform state is ensured by the fact that one of the electrodes (cathode) has a high resistance. The non-self-sustained Townsend discharge in the second gap is controlled by the state of the first gap, which is provided by a proper design of the device. The plasma-chemical anodic oxidation of a semiconductor in the microreactor is studied at room temperature while changing the current density and processing time. The thickness of the oxide films was determined by spectral ellipsometry and transmission electron microscopy. In accordance with the obtained data, the microreactor ensures the formation of nanoscale oxide layers, whose thickness can be varied by changing the parameters of the process. The results are compared with some literature data on dc gas-discharge anodic oxidation of GaAs. We believe that the method can be used in other plasma-chemical processes where gas-discharge products interact with a solid target.