This work describes doped-channel field-effect transistors (DCFETs), featuring both low-high doped-channels and double AIM etch-stop layers used in a selective etch recessed-gate process. A developed highly selective wet etching process is applied as a gate-recess technique to fabricate DCFETs. Selective wet etching using citric acid/H2O2/NH4OH/H2O solutions in conjunction with double thin AlAs etch-stop layers is a reasonably simple, safe, and reliable process for gate recessing in the fabrication of the DCFETs herein. Surface passivation using P2S5/(NH4)(2)S-x+ Se on GaAs Schottky barrier diodes, formed by Pt/Au contacts, is examined for the first time and the results are compared with those of unpassivated devices. For the passivated Pt/Au gate device, the two-terminal gate-drain breakdown (source floating) at -1 mA/mm is 17 V, and the device provides an excellent combination of transconductance and output current. The X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and photoluminescence results are highly consistent with the Schottky barrier measurements and the device performance. (C) 2011 Elsevier B.V. All rights reserved.