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We investigated 60-nm In0.52Al0.48As/In0.53Ga0.47As pseudomorphic high-electron mobility transistors (p-HEMTs) fabricated by using a Ne-based atomic-layer-etching (ALET) technology. The ALET process produced a reproducible etch rate of 1.47 Aring/cycle for an InP etch stop layer, an excellent InP etch selectivity of 70 against an In0.52Al0.48As barrier layer, and an rms surface-roughness value of 1.37 Aring for the exposed In0.52Al0.48As barrier after removing the InP etch stop layer. The application of the ALET technology for the gate recess of 60-nm In0.52Al0.48As/In0.53Ga0.47As p-HEMTs produced improved device parameters, including transconductance (GM), cutoff frequencies (fT)> and electron saturation velocity (vsat) in the channel layer, which is mainly due to the high etch selectivity and low plasma-induced damage to the gate area. The 60-nm In0.52Al0.48As/In0.53Ga0.47As p-HEMTs fabricated by using the ALET technology exhibited GM,Max = 1-17 S/mm, fT = 398 GHz, and vsat = 2.5 X 107 cm/s.
Date of Publication: July 2008