Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

Pristovsek, Markus; Bao, An; Oliver, Rachel A.; Badcock, T. J.; Ali, Muhammad; Shields, A. J.

doi:10.1103/physrevapplied.7.064007

Cited by 20 publications

(26 citation statements)

References 45 publications

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“…2(a), instead reporting large scatter across samples. 2,3 Following Ref. 16, we hypothesize that the values of A in some of those reports may in fact characterize carrier escape from the QW 17 and transport-related recombinations in defective heteroepitaxial LEDs, 6-8 rather than intrinsic NRR in the QW.…”

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confidence: 90%

Field-assisted Shockley-Read-Hall recombinations in III-nitride quantum wells

David

Hurni

Young

et al. 2017

Applied Physics Letters

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The physical process driving low-current non-radiative recombinations in high-quality III-Nitride quantum wells is investigated. Lifetime measurements reveal that these recombinations scale with the overlap of the electron and hole wavefunctions and show weak temperature dependence, in contrast with common empirical expectations for Shockley-Read-Hall recombinations. A model of field-assisted multiphonon point defect recombination in quantum wells is introduced, and shown to quantitatively explain the data. This study provides insight on the high efficiency of III-Nitride light emitters.Studies of the efficiency of III-Nitride light emitting diodes (LEDs) often focus on their high-current properties; insight into the physics of low-current and peak efficiency remains scarce. In particular, the demonstration of very efficient LEDs, despite the strong suppression of radiative recombination by polarization fields, 1 remains puzzling. Besides, the low-current regime is of crucial importance for basic physical understanding and for future application such as micro-LED displays.In this Letter, we study the physics of non-radiative recombination (NRR) in the low-injection regime -before the onset of current droop-in high-efficiency III-Nitride quantum well (QW) structures. With all-optical differential carrier lifetime measurements, we show that these recombinations display a strong dependence on the carrier wavefunctions in the QW and weak temperature dependence. These effects are quantitatively explained with a theory of field-assisted recombinations at point defects, driven by the polarization field across the QW.We first briefly review previous studies. In experiments, NRR is interpreted in the framework of ShockleyRead-Hall (SRH) theory where the NRR rate reads G N R = An, with n the carrier density and A an SRH coefficient whose value is fitted empirically, with reported values 2,3 of 10 5 − 10 8 s −1 -a wide range often explained away by invoking varying material quality. The currentdependence of the internal quantum efficiency is commonly described in the ABC model, with B the radiative coefficient and C interpreted as an Auger coefficient.On the theoretical front, first-principle studies have exposed the potential role of point defects as NRR centers and have computed corresponding SRH rates. 4,5 Yet, these calculations pertain to bulk materials, whereas the most relevant effect for LEDs is NRR in the QW active region. In device modeling, investigations are usually carried out in the drift-diffusion framework, using a constant and empirical SRH coefficient. Some device modeling studies have focused on the contribution of transport effects to low-current efficiency: they have shown the importance of trap-assisted tunneling processes (including free carriers tunneling across the junction and confined carriers escaping from the QW), which account for the a) Electronic mail: adavid@soraa.com high ideality factor often reported in III-Nitride LEDs at low current. 6-8 Yet, there as well, NRR inside the QW itself is ...

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confidence: 90%

Field-assisted Shockley-Read-Hall recombinations in III-nitride quantum wells

David

Hurni

Young

et al. 2017

Applied Physics Letters

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“…The emission of LEDs is commonly described by the ABC model. [1][2][3][4][5][6][7][8] In the ABC model, the carrier density n determines the probability of carriers encountering each other and thus the different recombination rates. Shockley-Read-Hall (SRH) nonradiative recombination is assumed as An (carriers meet a defect subsequently), the radiative recombination is Bn 2 (meeting of an electron with a hole), and the nonradiative Auger effect loss is Cn 3 (three carriers must meet).…”

Section: Fitting Of the Peak Iqementioning

confidence: 99%

Direct Determination of the Internal Quantum Efficiency of Light‐Emitting Diodes

Pristovsek

2022

Physica Rapid Research Ltrs

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The maximum internal quantum efficiency (IQE) of light‐emitting diodes (LEDs) can be obtained using the so‐called ABC model. Since the ABC model is based on the experimentally not directly accessible carrier density, the light over current data is usually fitted as a function of the light output to yield the maximum IQE. This article shows a method to directly obtain the IQE from experimental data without fitting, which also reflects changes of the A, B, or C parameters over the current range.

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“…Well-established growth processes with respect to growth temperature were employed. [43][44][45][46][47] Aer covering the LED layers with photoresist, holes were dened using electron-beam lithography and subsequent development. Aer the physical vapour deposition of Ni followed by a li-off process, Ni caps were formed, which served as the mask for the subsequent Ar-ion beam etching process.…”

Section: Materials and Sample Preparationmentioning

confidence: 99%