Dependence of microwave emission from indium antimonide on surface conditions and sample geometries

摘要

The dependence of microwave emission from n‐InSb on condition of the sample surface and the sample geometry has been investigated at average electrical field strengths lower than those necessary for avalanche breakdown to occur in the bulk of the sample. Results are interpreted in terms of the theory by Thompson and Kino, and King, by assuming that plasma is produced in regions of high fields near the contacts by end‐contact shorting of the Hall field. It is shown that the strong anisotropy of the emission, when the magnetic field is rotated in the transverse plane, is caused by surface inhomogeneities and can be controlled by deliberately changing the surface conditions. This anisotropy of the emission is interpreted by the influence of the magnetoresistance on the diffusion of electron‐hole pairs towards the surface of the sample. For a sample with circular cross section and properly etched surface, the emission is isotropic with respect to the position of the magnetic field in the azimutal plane. On the other hand, strong anisotropy is obtained for samples with rectangular cross section. The emission has been found to saturate with increasing sample length in accordance with the assumption that the contact regions play a predominant role. Samples with a Corbino‐shaped geometry do not show any emission due to the absence of high electric field regions at the contacts.