Self-aligned gate recess technology for the fabrication of InAlAs/InGaAs HEMT structures, using InAlAs as an etch-stop layer

A self-aligned gate recess technology for the fabrication of InAlAs/InGaAs HEMTs is discussed. The applied reactive ion etching (RIE) process has a selectivity for InGaAs over InAlAs of 6:1, allowing a thin InAlAs Schottky barrier layer. The self-aligned Ti/Au metallization is suitable for the reproducible fabrication of gate lengths down to 0.3 μm, starting with a 1 μm recess. Realized gate leakage currents of 100 nA at a reverse bias of 5 V show that no degradation of the Schottky barrier occurs due to the process technology. With first HEMTs a transconductance of 400 mS/mm and a cutoff frequency of 22 GHz have been achieved