Local internal quantum efficiency of a green light emitting InGaN/GaN quantum well

We describe a mechanism by which complexes between gallium vacancies and oxygen and/or hydrogen act as efficient channels for nonradiative recombination in InGaN alloys. Our identification is based on first-principles calculations of defect formation energies, charge-state transition levels, and nonradiative capture coefficients for electrons and holes. The dependence of these quantities on alloy composition is analyzed. We find that modest concentrations of the proposed defect complexes (∼1016 cm−3) can give rise to Shockley-Read-Hall coefficients A=(107−109) s−1. The resulting nonradiative recombination would significantly reduce the internal quantum efficiency of optoelectronic devices.

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Gallium vacancy complexes as a cause of Shockley-Read-Hall recombination in III-nitride light emitters

Dreyer

Alkauskas

Lyons

et al. 2016

Applied Physics Letters

102

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Time of carrier escape and recombination coefficients in InGaN quantum-well active regions of blue, cyan, and green light-emitting diodes

Reklaitis

Krencius

Malinauskas

et al. 2018

Semicond. Sci. Technol.

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Addressing the recently observed unexpected low-current saturation of differential carrier lifetime (DLT) in the active region of InGaN-based light-emitting diodes (LEDs), a novel procedure is suggested for the evaluation of both escape time of carriers from the InGaN quantum wells and their recombination coefficients. The procedure uses coupled measurements of external quantum efficiency and DLT as a function of LED continuous-wave operating current. The procedure has been applied to three LEDs with InGaN multiple quantum well (QW) active regions emitting blue, cyan, and green light. Laser diodes operating at different wavelengths were employed for small-signal resonant pumping of the LED active regions in order to understand a possible dependence of the escape time and recombination coefficients on the excitation wavelength. The revealed wavelength dependence of the Shockley-Read-Hall recombination coefficient in the green LED is attributed to lateral non-uniformity of the InGaN QW with high Indium content. The radiative and Auger recombination coefficients evaluated by the above procedures in all three LEDs turned out to be close to those reported earlier for the LEDs with single QW active regions. The obtained recombination coefficients are used for further performance comparison of the studied devices. The suggested procedure is helpful for the investigation of carrier escape and the optimization of III-nitride devices, such as photodetectors, solar cells, and quantum-cascade lasers.

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Calcium as a nonradiative recombination center in InGaN

Shen

Wickramaratne

Dreyer

et al. 2017

Appl. Phys. Express

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Calcium can be unintentionally incorporated during the growth of semiconductor devices. Using hybrid functional first-principles calculations, we assess the role of Ca impurities in GaN. Ca substituted on the cation site acts as a deep acceptor with a level ∼1 eV above the GaN valence-band maximum. We find that for Ca concentrations of 1017 cm−3, the Shockley–Read–Hall recombination coefficient, A, of InGaN exceeds 106 s−1 for band gaps less than 2.5 eV. A values of this magnitude can lead to significant reductions in the efficiency of light-emitting diodes.

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Local internal quantum efficiency of a green light emitting InGaN/GaN quantum well

Cited by 3 publications

References 19 publications

Gallium vacancy complexes as a cause of Shockley-Read-Hall recombination in III-nitride light emitters

Gallium vacancy complexes as a cause of Shockley-Read-Hall recombination in III-nitride light emitters

Time of carrier escape and recombination coefficients in InGaN quantum-well active regions of blue, cyan, and green light-emitting diodes

Calcium as a nonradiative recombination center in InGaN

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