Improving p-type contact characteristics by Ni-assisted annealing and effects on surface morphologic evolution of InGaN LED films grown on Si (1 1 1)

Ni thin layer was deposited to assist to activate p-GaN and then was removed. The process was named Ni-assisted annealing (NA). We investigate the surface morphology and p-type contact behaviors of InGaN LED films grown on Si (1 1 1) substrates. Compared with conventional thermal annealing (TA), NA can improve the p-type contact characteristic at lower anneal temperature and a smaller specific contact resistivity (ρc = 6.1 × 10−5 Ω cm2) employing nonalloy Pt electrode was obtained. A wet etching method using acid-hydrogen peroxide was adopted to boil films surface after activation. We found that some nano-pits appeared on surfaces while original surface step structure was still clearly visible, which shows a defect-selective etching characteristic. Otherwise, we demonstrated that the surface morphology could be affected by NA while independent to TA. Some mechanisms for experimental phenomena were also discussed in the letter.

► p-type specific contact resistivity can be reduced by Ni-assisted annealing. ► Ni-assisted annealing can promote interface reaction between GaN and Ni. ► Acid-hydrogen peroxide can be used to etch the interface defect-selectively. ► Pits formed on surface of p-GaN after etch in acid-hydrogen peroxide. ► Ni-assisted annealing can promote the forming and growth of pits.