Abstract
The optical properties of the InGaN/AlGaN light-emitting diodes(LEDs) with varied quantum well(QW) numbers are studied numerically.The simulated results show that the single quantum-well(SQW) structure has the best optical performance with small current less than 100 mA.However,the 9-QWs structure obtains higher output power and IQE than other structures when the current is larger than 700 mA,and the efficiency droop is dropped markedly from 14.10% to 5.15% at 700 mA comparing with that of the SQW structure.Therefore,9-QWs is the optimized structure for high-power LEDs.It can be explained as follows:(1) The 9-QWs structure acquires higher capacity of carrier confinement due to the smaller band bending effect and the effective hole potential barrier heights formed by the electron block layer(EBL).(2) When the QW number is less than 9,the lower capacity of carrier confinement and lower radiative recombination rate in the active region reduce the performance of the device,though the turn-on voltage is lower.(3) When the QW number is more than 9,the structure shows higher peak internal quantum efficiency(IQE) and less serious efficiency droop compared with 9-QW structure.However,the smaller IQE and larger band bending effect make it worse for a high power structure.
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