Injection and Avalanche Electroluminescence of $\hbox {Al}_{\hbox {0.1}} \hbox {Ga}_{\hbox {0.9}} \hbox {N/Al}_{\hbox {0.15}} \hbox {Ga}_{\hbox {0.85}} \hbox {N}$ Multi

Three periods of Al_0.1Ga_0.9N/Al_0.15Ga_0.85 N multiple quantum wells (MQWs) were used as the active region of a p-i-n diode fabricated on 6H-SiC substrate. Electroluminescence (EL) of these MQWs has been investigated in both injection and avalanche modes. Band-to-band luminescence of the Al_0.1Ga_0.9N wells was found to peak at 364 nm in the injection mode and in the range of 364-372 nm in the avalanche mode. The most striking phenomenon is that band-to-band EL of the Al_0.15Ga_0.85N barriers has also been observed in the injection mode, while it is not seen in the avalanche mode. This is explained by considering different sources of carriers and different carrier transportation mechanisms in the two modes. The luminescence intensity I _EL has a power-law dependence on the current I by I _EL prop I ² in the injection mode and by I _EL prop I ⁴ in the avalanche mode.