Investigation of dominant effect on efficiency droop in InGaN light emitting device

To understand a major effect on efficiency droop, radiative characteristics of InGaN laser diodes (LDs) of emission wavelength of ∼ 445 nm are studied at subthreshold levels for different active structures; (1) InGaN single quantum well (SQW), (2) double quantum wells (DQWs) with Si-doped barrier, and (3) DQWs with undoped barrier. For InGaN LDs with DQWs, the absolute radiative efficiency is most dominant for the case of undoped barrier, and least for the case of Si-doped barrier. The efficiency droop in InGaN LDs with DQWs, regardless of the doping condition of barriers, is typical of reported InGaN light emitting devices, whereas for the InGaN LD with SQW, the efficiency droop is significantly improved for all current density levels due to the least polarization field of InGaN QW.