Ohmic contacts to n-GaN using PtIn2

A new metallization scheme has been developed to form Ohmic contacts to n-GaN. Contacts were fabricated by sputtering the intermetallic compound, ${\mathrm{PtIn}}_2$ on metal–organic vapor phase epitaxy grown n-GaN ${\text{(n∼5×10}}^{17}\hspace{0.5em}{\mathrm{cm}}^{\text{−3}})$ with some of the contacts subjected to rapid thermal annealing. Contacts in the as-deposited state exhibited nearly Ohmic behavior with a specific contact resistance of ${\text{1.2×10}}^{\text{−2}}\mathrm{\hspace{0.5em}\Omega \hspace{0.17em}}{\mathrm{cm}}^2$ . Contacts subjected to rapid thermal annealing at 800 °C for 1 min exhibited linear current–voltage characteristics and had specific contact resistances less than ${\text{1×10}}^{\text{−3}}\mathrm{\hspace{0.5em}\Omega \hspace{0.17em}}{\mathrm{cm}}^2$ . Auger depth profiling and glancing angle x-ray diffraction were used to examine the interfacial reactions of the ${\mathrm{PtIn}}_2\mathrm{/n-}\mathrm{GaN}$ contacts. Consistent with estimated phase diagram information, the results from Auger depth profiling and glancing angle x-ray diffraction indicated the formation of $({\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}})\mathrm{N}$ at the contact interface, which could be responsible for the Ohmic behavior of ${\mathrm{PtIn}}_2$ contacts.