Influences of an electron reservoir layer on the optical and the electrical properties of InGaN/GaN MQW LEDs

We present the effect of an n-InGaN electron reservoir layer (ERL) on the optical and the electrical properties of InGaN/GaN multiple-quanturn-well (MQW) light-emitting diodes (LEDs). The optical and the electrical properties of the LED samples were investigated by using photolumi-nescence (PL), time-resolved PL (TRPL) and electroluminescence (EL) spectroscopy. The carrier lifetimes for the LED samples with the ERL structure were relatively longer than that for the LED sample without the ERL (reference sample). For an InGaN/GaN MQWs separated from the ERL structure by a 30-Å-thick GaN tunnel barrier, the decay time was 9.2 ns at 12 K, which was 1.23 times longer than that of the reference sample. Also, the light-output power for the LED with the ERL structure having a 20-Å-thick GaN tunnel barrier was 1.15 times stronger than that of the reference LED. The relatively longer carrier lifetime and the increase in the light-output power for the LED sample with the ERL structure can be attributed to the reduced electron overflowing, resulting in a decreased nonradiative recombination rate of the carriers in the InGaN/GaN MQW region.