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

An interesting Pd-AlGaN/GaN Schottky diode-type hydrogen sensor with ultrahigh sensing responses is fabricated and studied. A sensing response (S-F) of 2.04 x 10(5) and a widespread Schottky barrier height variation (Delta phi(B)) of 400 meV are observed upon exposure to a 9660 ppm H-2/air gas at 150 degrees 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 round to be 1.9 and 0.7 torr(-1) at 150 degrees C and 200 degrees C, respectively. The fast response and recovery times (< 10 s) are found under a 9660 ppm H-2/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.