Effects of nitride-based plasma pretreatment prior to SiN_x passivation in AlGaN/GaN high-electron-mobility transistors on silicon substrates

The effects of nitride-based plasma pretreatment on the output characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) on silicon substrates are investigated. N₂ and NH₃ plasma pre-treatment methods are studied to overcome the RF dispersion phenomenon caused by nitrogen-vacancy (V_N)-related defect reduction. It is found that the nitride-based plasma pretreatment is effective to overcome the RF dispersion in AlGaN/GaN HEMTs on Si. The NH₃ plasma pretreatment markedly reduced RF dispersion from 63 to 1%. This is considered to be attributable to the reduction of the effective V_N-related defect density and elimination of carbon/oxide residuals on the surface of AlGaN/GaN HEMTs. A NH₃ plasma pretreatment prior to SiN_x 100nm passivation in the AlGaN/GaN HEMTs on Si markedly improves the total output power from 15 to 18.1 dBm under the operating conditions of V_DS = 15 V/V_GS = -1 V.