Uniform InAlAs/InP HFET fabricated using selective dry recess etching

Low-frequency noise measurements are used as a diagnostic tool in order to assess the quality of CH4/H2 dry recess etching applied to InAlAs/InP heterojunction field effect transistors (HFETs). Devices recessed with conventional wet chemical etching exhibit higher excess noise when compared with the reactive ion etching (RIE) devices. The experimentally observed relative noise in the drain current SId/Id2 biased at low drain voltage versus the effective gate voltage Vg = Vgs − Vp shows the same behaviour on both devices. We find that the noise can be explained by noise fluctuations in the series resistances RGS and RGD the source and drain side of the channel, respectively, and noise fluctuations in the channel Rch. Dry-etched devices exhibit low series resistances (1.6 Ω mm) compared to wet-etched devices (2.4 Ω mm). The improvement of the noise spectra for the dry-etched devices can be explained by the reduction of the series resistances noise, which is due to the decrease of the series resistances.