A new Pd/AlGaN/GaN Schottky diode-type hydrogen sensor with pyramid-like Pd nanostructures is fabricated and studied comprehensively. The employed pyramid-like Pd nanostructures cause the substantial increase of surface roughness and surface-to-volume aspect ratio which give the remarkable increase of adsorption sites on the surface for hydrogen molecules. Experimentally, the studied device with pyramid-like Pd nanostructures demonstrates enhanced hydrogen sensing performance, including a large forward-bias current variation of 1.95 x 10(-6) A and a high sensing response of 1454 under an introduced 1% H-2/air gas at 300 K. These properties are remarkably superior to those of the conventional planar-surface device. In addition, an improved hydrogen detection limit of 10 ppb H-2/air at 300 K is found for the studied device with pyramid-like Pd nanostructures. The related hydrogen sensing characteristics including transient responses and steady-state analysis are also studied in this work. Therefore, based on the improved sensing properties and advantages of low-cost, easy fabrication, and solid stability of operation, the studied device shows the promise for high-performance hydrogen sensing applications. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.