Impact of the forward bias on the radiative recombination efficiency in blue (In,Ga)N/GaN quantum-well diodes with an electron reservoir layer

The temperature dependence of the electroluminescence (EL) spectral intensity between T= 20 and 300 K has been investigated in detail for two blue (In,Ga)N/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) without and with an additional n-doped In_0.18Ga_0.82N electron reservoir layer (ERL). The radiative recombination efficiency significantly changes, when the additional ERL is introduced. For high injection currents I_f i.e., large forward bias voltages V_f a quenching of the EL intensity is observed for T<100 K. Furthermore, the temperature variation of the EL intensity is stronger for the LED without the ERL than for the LED with the ERL. For low I_f, i. e., small V_f, however, no quenching of the EL intensity is observed for both LEDs even below 100 K due to efficient carrier capture. These results imply that the unusual evolution of the EL intensity with T and If is probably caused by variations of the actual potential field distribution due to both internal and external fields, which significantly influence the carrier capture efficiency within the MQW layer.