Low contact resistivity between Ni/Au and p-GaN through thin heavily Mg-doped p-GaN and p-InGaN compound contact layer

Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p⁺⁺-InGaN layer is 10.6% and the thickness of p⁺⁺-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98×10^-5Ω·cm² is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07×10^-7Ω ·cm² by optimizing the alloying annealing temperature to 520 ℃.