Velocity-fluctuation noise in semiconductor layers and in MESFET channels under hot-electron conditions

The power spectral density of velocity-fluctuation noise in a semiconductor layer, or in the channel of a MESFET device, in the presence of a biasing electric field creating hot-eletron conditions, is calculated from the nonlinear dc current-voltage characteristic of the semiconductor existing under those conditions, by the use of Gupta´s nonlinear thermal noise theorem. The calculated results are shown to agree with measured noise temperatures for a variety of devices, at microwave frequencies and at moderately high electric fields. An empirical result relating the excess noise temperature in GaAs to the electric field is proposed.