We discovered that adding H2 to the carrier gas in GaN barrier growth improved the light emitting diode (LED) peak quantum efficiency and shifted the efficiency maxima toward lower currents (∼20 mA). This implies that the Shockley–Read–Hall nonradiative process can be suppressed via the introduction of combination carrier gas (H2/N2) during barrier growth. Further, 1–2 nm thick Al-In-Ga-N alloys were adopted as capping layers to circumvent H2 etching effect during growth interruption. It was then revealed that quantum efficiency was effectively enhanced for LEDs employed with these thin large bandgap capping layers, particularly at low injection levels. Numerical simulation suggested that the improved quantum efficiency can be ascribed to the increased electron capture rate in the active region as well as enhanced electron and hole wavefunction overlap, which correlated well with experimental results.
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