Abstract
GaN-based green light-emitting diodes (LEDs) with different thicknesses of the low-temperature (LT) p-GaN layer between the last GaN barriers and p-AlGaN electron blocking layer were characterized by photoluminescence (PL) and electroluminescence (EL) spectroscopic methods in the temperature range of 6–300 K and injection current range of 0.01–350 mA. Based on the results, we suggest that a 20 nm-thick LT p-GaN layer can effectively prevent indium (In) re-evaporation, improve the quantum-confined Stark effect in the last quantum well (QW) of the active region, and finally reduce the efficiency droop by about 7%.
Highlights
GaN-based light-emitting diodes (LEDs), one of the most important optoelectronic devices, have attracted much attention owing to significant progress in related material growth and device manufacturing fields [1,2,3,4,5]
InGaN-based LEDs emitting light of a longer wavelength in the green/yellow spectral range usually suffer from reduced emission efficiency, which is known as the green gap [8,9,10]
The variation in the PL peak energy and line width at different temperatures can be attributed to the conversion of carrier transfer mechanisms [23,24]
Summary
GaN-based light-emitting diodes (LEDs), one of the most important optoelectronic devices, have attracted much attention owing to significant progress in related material growth and device manufacturing fields [1,2,3,4,5]. The external quantum efficiency (EQE) of high-performance GaN-based LEDs has been recorded to exceed 80%, and they have been extensively used in applications such as general illumination, displays, and communications [6,7]. InGaN-based LEDs emitting light of a longer wavelength in the green/yellow spectral range usually suffer from reduced emission efficiency, which is known as the green gap [8,9,10]. Since the first reports of green light-emitting InGaN LEDs, these devices have been used in a variety of commercial applications [11,12,13,14]. Green LEDs suffer from a reduction in EL efficiency under high injection currents, which is known as “efficiency droop”.
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