Carrier lifetimes in polar InGaN-based LEDs

Lai Wang; Jie Jin; Zhibiao Hao; Yi Luo

doi:10.1117/12.2286022

23 February 2018 Carrier lifetimes in polar InGaN-based LEDs

Lai Wang, Jie Jin, Zhibiao Hao, Yi Luo

Proceedings Volume 10532, Gallium Nitride Materials and Devices XIII; 105321Q (2018) https://doi.org/10.1117/12.2286022
Event: SPIE OPTO, 2018, San Francisco, California, United States

Abstract

Measurement of carrier lifetime is very important to understand the physics in light-emitting diodes (LEDs), as it builds a link between carrier concentration and excitation power or current density. In this paper, we present our study on optical and electrical characterizations on carrier lifetimes in polar InGaN-based LEDs. First, a carrier rate equation model is proposed to explain the non-exponential nature of time-resolved photoluminescence (TRPL) decay curves, wherein exciton recombination is replaced by bimolecular recombination, considering the influence of polarization field on electron-hole pairs. Then, nonradiative recombination and radiative recombination coefficients can be deduced from fitting and used to calculate the radiative recombination efficiency. By comparing with the temperature-dependent photoluminescence (TDPL) and power-dependent photoluminescence (PDPL), it is found these three methods provide the consistent results. Second, differential carrier lifetimes depending on injection current are measured in commercial near-ultraviolet (NUV), blue and green LEDs. It is found that carrier lifetime is longer in green one and shorter in NUV one, which is attributed to the influence of polarization-induced quantum confined Stark effect (QCSE). This result implies the carrier density is higher in green LED while lower NUV LED, even the injection current is the same. By ignoring Auger recombination and fitting the efficiency–current and carrier lifetime–current curves simultaneously, the dependence of injection efficiency on carrier concentration in different LED samples are plotted. The NUV LED, which has the shallowest InGaN quantum well, actually exhibits the most serious efficiency droop versus carrier concentration. Then, the approaches to overcome the efficiency droop are discussed.

Citation Download Citation

Lai Wang, Jie Jin, Zhibiao Hao, and Yi Luo "Carrier lifetimes in polar InGaN-based LEDs", Proc. SPIE 10532, Gallium Nitride Materials and Devices XIII, 105321Q (23 February 2018); https://doi.org/10.1117/12.2286022

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KEYWORDS

Light emitting diodes

Green light emitting diodes

Quantum wells

Internal quantum efficiency

Indium gallium nitride

Luminescence

Polarization

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