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The measured photo-excited external quantum efficiency, absolute internal quantum efficiency, and carrier density of sample A (open diamonds, thin solid line, thick solid line) and sample E (closed circles, dashed thin line, dashed thick line) vs excitation level. The measured external quantum efficiency is fit with the , , and coefficients listed in Table I to yield the absolute internal quantum efficiency scale. The carrier density at peak efficiency is . In the inset, a Poisson-Schrodinger simulated band diagram shows that flat band conditions prevail in quasi-bulk InGaN layer at excitation levels used for this measurement.
Photoluminescence decay (log of light output vs time) of sample A. The thin solid line is the simulated decay using the , , and coefficients determined iteratively from fitting the photoluminescence decay and quantum efficiency vs excitation simultaneously. In the inset is plotted emission spectrum of sample A at different excitation densities (q=3.64, 2.29, 1.15, 0.87, 0.55, 0.39, 0.26, 0.19, 0.11 ). The peak efficiency is at q=0.39 (thick solid line). The laser excitation appears at 378 nm. No exciton peaks appear in the spectra, and the peak wavelengths stay at . The thin straight line is a Boltzmann tail fit showing that the carrier temperature () is not more than 550 K at the highest excitation densities, which are well beyond the level where the peak efficiency is observed.
List of InGaN layer properties: InN%, (thickness), and TDD (threading dislocation density). The (Shockley-Read-Hall), (radiative recombination), and (Auger) coefficients are determined from fits of the photoluminescence quantum efficiency and decay.
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