Abstract
A semi-empirical model of carrier recombination accounting for hole localization by composition fluctuations in InGaN alloys is extended to polar and nonpolar quantum-well structures. The model provides quantitative agreement with available data on wavelength-dependent radiative and Auger recombination coefficients in polar LEDs. Comparison of calculated internal quantum efficiencies of polar and nonpolar LEDs enables an assessment of the roles of carrier localization, quantum-confined Stark effect, and native material properties for the efficiency decline in the “green gap”.
Highlights
Recent progress in growth and fabrication technology has enabled the demonstration ofInGaN-based light-emitting diodes (LEDs) with maximum external quantum efficiency (EQE) over~80% in the violet-blue spectral range [1,2]
In order to compare the theory with the experiment, the data on wavelength‐dependent radiative recombination coefficient (RRC) and Auger recombination coefficient (ARC) from [20] have been chosen as those providing the best correlation with independently estimated internal quantum efficiency (IQE) of state‐of‐the‐art LEDs
A semi-empirical model accounting for hole localization by InGaN composition fluctuations has been extended to quantum wells (QWs) of polar and nonpolar orientations
Summary
Recent progress in growth and fabrication technology has enabled the demonstration ofInGaN-based light-emitting diodes (LEDs) with maximum external quantum efficiency (EQE) over~80% in the violet-blue spectral range [1,2]. The maximum EQE values of LEDs operating in the green, ~40–50% [7,8], and yellow, ~20% [9], spectral ranges are remarkably lower than that in the violet/blue one, which cannot be attributed to insufficient light extraction from the LED dice [10]. A remarkable increase in the threshold current density and decrease in the wall-plug efficiency of InGaN-based laser diodes is observed in the same spectral range [11,12]. These “green gap” manifestations in both LEDs and laser diodes imply their common nature, pointing to some internal processes in the InGaN active regions
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