Formation of Ti/Al ohmic contacts on Si-doped GaN epilayers by low temperature annealing

Ohmic contacts have been fabricated on Si-doped GaN using Ti/Al by low temp erature annealing at 500 degrees C. A contact resistivity of 8.6 x 10(-6) o hm cm(2) was obtained for n-GaN samples doped to 3.67 x 10(18) cm(-3). Seco ndary ion mass spectrometry (SIMS) analysis showed that Al diffused through the Ti layer after annealing. Furthermore, energy dispersive x-ray spectro scopy (EDS) analysis showed that reaction products of Al, Ti, Ga and N were present at the interface. Hence, a complex ternary or quaternary nitride a s a possible low barrier height material to n-GaN may have resulted in good ohmic contact. Photoluminescence (PL) showed that there was no degradation in the epilayer quality of the film after annealing at 500 degrees C for 2 5 minutes.