[21a-P06-1~17] 13.7 Compound and power devices, process technology and characterization

English Presentation

[21a-P06-15] Annealing temperature dependence of In/Au electrode performance on p-GaN

〇MariaEmma Castil Villamin¹, Naotaka Iwata¹ (1.Toyota Tech Inst)

Keywords:

low temperature contact annealing,pGaN ohmic,In/Au metal

Electrode formation with low contact resistance on p-GaN is a rigid demand for improved performance of p-GaN gate power HEMT as well as for realization of C-MOS integrated GaN devices. In addition, excimer laser annealing has been explored due to its capability of localized activation of p-type region on Mg-doped GaN layer for realization of vertical GaN power devices. However, low-temperature annealed contact is needed because high temperature annealing could result to unintended activation of Mg, surface degradation and thermal damage to the p-GaN layer. This study aims to investigate using circular transmission line measurement (CTLM) and material surface morphology the In/Au contact with different In thickness in the formation of low-temperature contact for laser-activated pGaN devices. It is found that the resistivity decreases when the In thickness was increased. At high annealing temperature, the resistivity is very high implying that surface might be damaged. Under optical microscope, for thin In sample, at 750°C the In/Au contact appears transparent implying that the In diffuses into the wafer. In conclusion, we have successfully investigated the surface and the contact resistance of the In/Au contact with different In thickness using Mg-doped of 10¹⁸cm^-3 GaN samples. In the future, additional metal barrier e.g. Ti can be also used to better optimized contact.