Noise and microscopic defects in electron bombarded junction field effect transistors

The effects of electron bombardment on the noise in junction field effect transistors (JFETs) were studied, using a 3 MeV van de Graaff accelerator as the source of electron radiation. As the noise in a JFET can be characterized by the short circuit noise resistance, the noise conductance, and correlation conductance, quantitative changes in the values of these parameters, which arise as a result of electron bombardment, were evaluated. This was accomplished by using the pre- and post-irradiation noise figure characteristics at 100 and 600 KHz, measured over a wide range of source resistances from 300 omega to 745 K omega. It is shown by a systematic analysis of the changes in the noise parameters that noise resistance is the most sensitive noise parameter to electron bombardment and this is attributed to a large increase of generation-recombination (g-r) noise in irradiated JFETs. The large increase of g-r noise is confirmed by means of the frequency spectra of noise in irradiated JFETs, which exhibit well defined time constants, an important characteristic of g-r noise.