In this article, the hydrogen sensing characteristics of Al0.25Ga0.25In0.5P/In0.1Ga0.9As enhancement/depletion-mode co-integrated pseudomorphic doping-channel field-effect transistors by wet selectively etching process are demonstrated. At drain current of 0.1 mA/mm, the threshold voltages are of -0.97 (+0.6) V and -1.22 (+0.31) V in air and at hydrogen concentration of 9800 ppm, respectively, for the depletion (enhancement)-mode device. In addition, by employing the co-integrated FETs the transfer characteristics of the direct-coupled FET logic (DCFL) obviously vary under hydrogen ambience. The V-OH value reduces and the V-OL value increases in the DCFL with the measurement of hydrogen detection. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.