Low frequency noise in dry and wet etched InAlAs/InGaAs HEMTs

The low frequency noise of lattice-matched InP-based HEMTs gate recess etched with CH/sub 4//H/sub 2/ RIE and phosphoric-acid based wet etchants was studied at different gate and drain biases in a temperature range of 77 K to 340 K. The measurements showed a significantly lower normalized drain current 1/f noise for the dry etched HEMTs in all bias conditions. Varying the temperature, four electron traps could be identified in the drain current noise spectra for both dry and wet etched devices. No additional traps were introduced through the dry etching step. The concentration of the main trap in the Schottky layer is one order of magnitude lower for the dry etched HEMTs probably due to hydrogen trap passivation. The kink effect in the dry etched HEMTs was observed to be reduced significantly compared with wet etched devices which gives further evidence of trap passivation during dry etching.