Abstract: The effects of surface passivation on AlGaN/GaN highelectronmobility transistors (HEMTs) have been investigated. The surface passivation layer of Si₃N₄ is deposited by plasma enhanced chemical vapor deposition (PECVD). The currentvoltage and gatedrain diode characteristics of AlGaN/GaN HEMTs before and after passivation are analyzed. The current collapse under DC sweep has been significantly decreased after passivation and the existence of small dispersion of drain current is due to traps in the GaN buffer. The drain current increases after passivation, because surface passivation reduces the surface state density and so increases the sheet carrier density shown in Transmission Linear Model (TLM) measurement.

Key words: high electron mobility transistors, passivation, current collapse