Matthias Auf der Maur

arXiv2024

Empirical tight-binding method for large-supercell simulations of disordered semiconductor alloys

We analyze and present applications of a recently proposed empirical tight-binding scheme for investigating the effects of alloy disorder on various electronic and optical properties of semiconductor alloys, such as the band gap variation, the localization of charge carriers, and the optical transitions. The results for a typical antimony-containing III-V alloy, GaAsSb, show that the new scheme greatly improves the accuracy in reproducing the experimental alloy band gaps compared to other widely used schemes. The atomistic nature of the empirical tight-binding approach paired with a reliable parameterization enables more detailed physical insights into the effects of disorder in alloyed materials.

cond-mat.mtrl-sci↗

arXiv2015

Unraveling the "Green Gap" problem: The role of random alloy fluctuations in InGaN/GaN light emitting diodes

White light emitting diodes based on III-nitride InGaN/GaN quantum wells currently offer the highest overall efficiency for solid state lighting applications. Although current phosphor-converted white LEDs have high electricity-to-light conversion efficiencies, it has been recently pointed out that the full potential of solid state lighting could be exploited only by color mixing approaches without employing phosphor-based wavelength conversion. Such an approach requires direct emitting LEDs of different colors, in particular in the green/yellow range ov the visible spectrum. This range, however, suffers from a systematic drop in efficiency, known as the "green gap", whose physical origin has not been understood completely so far. In this work we show by atomistic simulations that a consistent part of the "green gap" in c-plane InGaN/GaN based light emitting diodes may be attributed to a decrease in the radiative recombination coefficient with increasing Indium content due to random fluctuations of the Indium concentration naturally present in any InGaN alloy.

cond-mat.mtrl-sci↗