Investigation on a Pd–AlGaN/GaN Schottky Diode-Type Hydrogen Sensor With Ultrahigh Sensing Responses

摘要

An interesting Pd–AlGaN/GaN Schottky diode-type hydrogen sensor with ultrahigh sensing responses is fabricated and studied. A sensing response $(S_{F})$ of $hbox{2.04} times hbox{10}^{5}$ and a widespread Schottky barrier height variation $(Deltaphi_{B})$ of 400 meV are observed upon exposure to a 9660 ppm $hbox{H}_{2}/hbox{air}$ gas at 150 $^{circ}hbox{C}$. The high sensing response can be attributed to the catalytic capability of Pd metal with contributions from a high-density 2-D electron gas induced from spontaneous and piezoelectric polarizations. From a Langmuir isotherm, the equilibrium constants are found to be 1.9 and 0.7 $hbox{torr}^{-1}$ at 150 $^{circ}hbox{C}$ and 200 $^{ circ}hbox{C}$, respectively. The fast response and recovery times ( $≪$ 10 s) are found under a 9660 ppm $hbox{H}_{2}/ hbox{air}$ gas. Consequently, the compatible process of the AlGaN/GaN sensor makes it possible to be integrated into other high-sensing performance sensor for microelectrical and mechanical applications.