Operation-induced short-term degradation mechanisms of 275-nm-band AlGaN-based deep-ultraviolet light-emitting diodes on a sapphire substrate

Degradation mechanisms of 275-nm-band AlGaN quantum well deep-ultraviolet light-emitting diodes fabricated on a (0001) sapphire substrate were investigated under hard operation conditions. The optical output power (Po) initially decreased by about 20 % within the operating time less than 102 h and then gradually decreased to about 60 % by 484 h. Because the degradation of the wells was less significant than the Po reduction, the initial degradation is attributed essentially to the decrease in carrier injection efficiency, most likely due to de-passivation of initially H-passivated preexisting nonradiative recombination centers (NRCs) in a Mg-doped p-type Al0.85Ga0.15N electron blocking layer. According to our database on the species of vacancy-type defects acting as NRCs in GaN and AlN, vacancy clusters comprised of a cation vacancy and nitrogen vacancies are the most suspicious origins of the NRCs.