Reversible barrier height changes in hydrogen-sensitive Pd/GaN and Pt/GaN diodes

The forward current of Pd/GaN and Pt/GaN Schottky diodes is found to increase significantly upon introduction of ${\mathrm{H}}_2$ into a ${\mathrm{N}}_2$ ambient. Analysis of the current–voltage characteristics as a function of temperature showed that the current increase is due to a decrease in effective barrier height through a decrease in metal work function upon absorption of hydrogen. The introduction of 10% ${\mathrm{H}}_2$ into a ${\mathrm{N}}_2$ ambient was found to lower the effective barrier height of Pd on GaN by $\text{50∼70\hspace{0.17em}}\mathrm{meV}$ over the temperature range of 298 to $\text{∼423\hspace{0.17em}}\mathrm{K}$ and of Pt on GaN by $\text{30∼60\hspace{0.17em}}\mathrm{meV}$ over the range of 443 to $\text{∼473\hspace{0.17em}}\mathrm{K}.$ The magnitude of the changes increased with temperature due to the effective cracking of the ${\mathrm{H}}_2.$ The changes in barrier height were completely reversible upon restoration of ${\mathrm{N}}_2$ ambient.