Optical properties of c -Plane InGaN/GaN single quantum wells as a function of total electric field strength

A series of single InGaN/GaN quantum wells with a Si-doped InGaN underlayer were studied to investigate the impact of the underlayer on photoluminescence efficiency and recombination dynamics. The thickness of the GaN capping layer was varied between samples, which changed the electric field across the QW due to band bending near the surface. When directly exciting the wells, thermionic emission of carriers results in a rapid drop in the photoluminesence efficiency with increasing temperature such that no emission is observed above 100 K. However, exciting above the energy of the barriers caused the intensity of the QW emission to drop more slowly, with up to 12 % of the 10 K emission intensity remaining at 300 K. This difference is attributed to hole transfer from the underlayer into the quantum well, which increases in efficiency at higher temperatures, and is enhanced by stronger electric fields present in the GaN barriers of samples with thinner GaN capping layers. Further, the sample with the narrowest cap layer of 2 nm has a different shape and characteristic time for its photoluminescence decay transient and a different emission energy temperature dependence than the other samples. This behaviour was ascribed to a change in carrier localisation for this sample due to a reversal of the net field across the well compared to the other samples.

Section: Resultssupporting

confidence: 94%

Section: Resultssupporting

confidence: 94%

Section: Resultssupporting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Si-doped InGaN underlayers on photoluminescence efficiency and recombination dynamics in InGaN/GaN quantum wells

Church

Christian²,

Barrett

et al. 2021

Effect of horizontal p–n junction on optoelectronics characteristics in InGaN-based light-emitting diodes with V-shaped pits

Gao¹,

Zhang²,

Quan³

et al. 2020

Two InGaN-based light-emitting diodes (LEDs) with and without pre-layer were prepared, and both had a similar multi-quantum well (MQW) structure with four green QWs near n-GaN and one blue QW close to p-GaN. The pre-layer established large V-shaped pits in MQWs. In addition to the regular vertical p-n junction along c-axis, a kind of horizontal p-n junction created by n-type MQWs and p-GaN filled in V-shaped pits was introduced. And the effect of the horizontal p-n junction on optoelectronics characteristics, including photoluminescence, electroluminescence, and I-V, were discussed. The horizontal p-n junction creates a strong horizontal built-in electric field which can effectively separate the photogenerated carriers in the QW close to p-GaN, leading to the absence of photoluminescence from the QW close to p-GaN. The horizontal p-n junction also provides a path for hole injection, which changes the turn-on order of QW, and reduces the voltage of the LED with large V-shaped pits. These results suggest a new thought of analyzing and designing InGaN-based LEDs with V-shaped pits.

Carrier density dependent Auger recombination in c-plane (In,Ga)N/GaN quantum wells: insights from atomistic calculations

McMahon,

Kioupakis,

Schulz

2023

Self Cite

Understanding Auger recombination in (In,Ga)N-based quantum wells is of central importance to unravelling the experimentally observed efficiency ‘droop’ in modern (In,Ga)N light emitting diodes (LEDs). While there have been conflicting results in the literature about the importance of non-radiative Auger recombination processes for the droop phenomenon, it has been discussed that alloy fluctuations strongly enhance the Auger rate. However, these studies were often focused on bulk systems, not quantum wells, which lie at the heart of (In,Ga)N-based LEDs. In this study, we present an atomistic analysis of the carrier density dependence of the Auger recombination coefficients in (In,Ga)N/GaN quantum wells. The model accounts for random alloy fluctuations, the connected carrier localisation effects, and carrier density dependent screening of the built-in polarisation fields. Our studies reveal that at low temperatures and low carrier densities the calculated Auger coefficients are strongly dependent on the alloy microstructure. However, at elevated temperatures and carrier densities, where the localised states are starting to be saturated, the different alloy configurations studied give (very) similar Auger coefficients. We find that over the range of carrier densities investigated, the contribution of the electron-electron–hole related Auger process is of secondary importance compared to the hole-hole-electron process. Overall, for higher temperatures and carrier densities, our calculated total Auger coefficients are in excess of 10−31 cm6 s−1 and may reach 10−30 cm6 s−1, which, based on current understanding in the literature, is sufficient to result in a significant efficiency droop. Thus, our results are indicative of Auger recombination being an important contributor to the efficiency droop in (In,Ga)N-based light emitters even without defect-assisted processes.