Stability of Al/Ti/Au contacts to N-polar n-GaN of GaN based vertical light emitting diode on silicon substrate

The electrical characteristics of Al/Ti/Au contact to N-polar n-GaN on Si substrate are investigated. It was found that a pre-treatment to the surface with Ar plasma could significantly enhance the stability of Al/Ti/Au contact. Forward voltage of the pre-treated sample was stabilized at about 3.23 V upon 1000 h aging under 900 mA and room temperature. In contrast, forward voltage of the untreated sample increased from 3.52 V to 4 V after 24 h aging. Those differences between the Ar plasma treated sample and untreated sample were attributed to the increase of the VN concentrate near surface of n-GaN by the Ar plasma treatment.