Low excess noise of InAlAs/InP HFETs fabricated using selective dry recess etching

The low frequency noise (10 Hz-100 kHz) behaviour of InAlAs/InP HFETs fabricated using CH₄/H₂ selective dry recess etching is reported. Devices from the same epitaxial structure fabricated using wet recess etching are also presented for comparison. The dry etching technique improves the drain noise spectral density. This improvement is attributed to the decrease in the source and drain resistance from 2.4 Ω mm for the wet recess, to 1.6 Ω mm For the dry recess. The equivalent series resistance fluctuations can explain the noise behaviour in both devices. No significant passivation of traps occurs during the CH₄/H₂ etching process, as demonstrated by noise measurements on annealed dry etched devices