A comparison of low- and high-frequency noise spectra of 0.1 micron gate-length conventional, pseudomorphic, and planar-doped MODFET structures

Abstract

In Modulation-doped FETs and MESFETs, as the gatelength is reduced, the generation-recombination (g-r) noise and l / f noise spectral intensities usually increase, whereas the thermal noise at high frequencies tends t o decrease. Thus the lower corner frequency (fc), where the LF noise intercepts with the extrapolated HF noise. moves steadily into higher frequencies. This report sh6ws that. through better device structure design, the impact of LF noise on the microwave and millimeter-wave performance can be minimized. It is also shown that inherently low thermal noise is attainable in MODFETs. INTRODUCTIONWe investigated the noise performance of various device designs in order t o correlate the LF noise and millimeter-wave noise performance to the circuit parameters of the device. Through this, we find that the g-r noise usually responsible for the higher f c observed in most MODFETs is reduced in one case of the planar-doped MODFET structure.The reduced g-r noise allows the identification of the l / f noise component in the LF noise spectrum. The l / f noise has been suggested t o be due to the quantization of energy loss by Umklapp scat-