Measurements of Electrical Transport Phenomena in Semiconductor Materials

摘要

In the experiment, a microwave-modulated electron beam bombards a reverse-biased semi-transparent rectifying contact on the surface of a low-doped epitaxial layer, creating secondary carriers which traverse the layer and are collected at the conducting substrate. Analysis of the ensuing periodic microwave current yields the carrier velocity as a function of electric field. A general theory is presented from which expressions relating the carrier velocity as a function of depth to the amplitude and phase of each component of the test device terminal current are derived. The consequences of electric field nonuniformity in the sample are examined, and a method developed to correct for this effect. Diffusion effects are evaluated with a one-dimensional numerical simulation of carrier motion through a test device, duplicating experimental conditions. All other relevant secondary effects, including beam penetration depth, circuit effects, trapping, sample heating, impact ionization, and space-charge effects, are examined in the context of the present work.