Ohmic contact to p-GaN using a strained InGaN contact layer and its thermal stability

We have formed ohmic contacts to p-GaN using a strained p-InGaN contact layer, and achieved the lowest contact resistance of 1.1 × 10^-6 Ω-cm² at room temperature by optimizing the contact layer thickness and its In mole fraction. We have also evaluated thermal stability of ohmic contacts to p-GaN using the strained p-InGaN contact layer. The contact resistance decreased to 2 × 10^-7 Ω-cm² at 100 C, and increased with elevating temperature above 100°C. In the temperature range up to 400 C, the contact resistances of the samples with the p-InGaN contact layer were smaller than those of the samples without the contact layer. Furthermore, the ohmic characteristics of the strained p-InGaN contact layer were less degraded even after the thermal process, compared with those of the sample without a contact layer. These results indicate that the strained p-InGaN contact layer is favorable for practical application.