A simple and convenient method for the formation of Pt nanoparticulate films as a sensing material by controlling deposition rates is demonstrated to realize AlGaN/GaN high electron mobility transistor-based high-sensitivity hydrogen gas sensors. The Pt nanoparticulate films produced at a low deposition rate (Sample 1: 0.3 Å/s) exhibit a smooth surface and uniformly sized Pt grains, while the films produced at a high deposition rate (Sample 2: 1.5 Å/s) consist of bigger Pt grains and more coalesced grains on the surface. The deposition rate has a distinct effect on the surface morphology. The maximum current change percentage for sample 1 is 2.1×10³% at a VGS of -4.3 V while that for sample 2 is 4.4×10³% at a VGS of -4.5 V. Sample 2 has a two times larger current response to hydrogen gas than sample 1, which results from a large increase in channel conduction induced by a huge catalytic surface area of Pt nanoparticulate films. This technique offers an alternative method for the facile deposition of a sensing material and is potentially useful in various applications, such as gas, chemical, and biological sensors.