Performance of High-Power AlInGaN Light Emitting Diodes

Abstract

The performance of high-power AlInGaN light emitting diodes (LEDs) is characterized by light output-current-voltage (L-I-V) measurements for devices with peak emission wavelengths ranging from 428 to 545 nm. The highest external quantum efficiency (EQE) is measured for short wavelength LEDs (428 nm) at %29%. EQE decreases with increasing wavelength, reaching %13% at 527 nm. With low forward voltages ranging from %3.3 to %2.9 V at a drive current density of 50 A/cm 2 , these LEDs exhibit power conversion efficiencies ranging from %26% (428 nm) to %10% (527 nm).Introduction With recent improvements in AlInGaN materials and device quality, visible blue and green light emitting diodes (LEDs) based on the AlInGaN material system have reached power conversion efficiencies that have surpassed those of conventional light sources. These LEDs are approaching the efficiencies of modern halogen and compact fluorescent lamps [1]. Together with yellow and red AlInGaP-based LEDs, for which luminous efficiencies >100 lm/W (%610 nm) have been reported [2], AlInGaN LEDs have become the light source of choice for applications where low energy consumption and long life are required. General illumination based on "white" LEDs that use either AlInGaN LED-based phosphor conversion or a combination of red, green and blue (RGB) LED chips is rapidly emerging.The brightness or quality of an LED is often characterized by quoting the external quantum efficiency (EQE), which is given by

Enhanced performance of GaN-based light-emitting diodes by using a p-InAlGaN/GaN superlattice as electron blocking layer

“…This well-known phenomenon is referred to as the efficiency droop. So far, there are several mechanisms considered to be responsible for the efficiency droop, such as the leakage current resulting from the piezoelectric effect [4], Auger recombination [5], junction heating [6], and carrier delocalization from the indiumrich region [7]. It was also reported that electron overflow plays a major role in the efficiency droop of GaN-based LEDs at high current density [8].…”

Reduction of efficiency droop in GaInN/GaN light-emitting diodes with thick AlGaN cladding layers

“…Although the root cause of the efficiency droop is not completely understood, many researchers agree with that it is related to the properties of GaN-based materials and their epitaxial structures. Recently numbers of physical origins of the efficiency droop were suggested, such as electron leakage from the active region, [1][2][3][4] Auger recombination, [5,6] lack of hole injection, [7][8][9] carrier delocalization, [10][11][12] and junction heating. [13] Kim et al suggested that polarization fields in the active region and the electron-blocking layer (EBL) facilitate the leakage of injected electrons into the p-type GaN layer where electrons and holes recombine nonradiatively, resulting in the efficiency droop.…”

Blue InGaN Light-Emitting Diodes With Multiple GaN-InGaN Barriers

“…Furthurmore, the problem of electron leakage is one of the major problems at high current density due to the piezoelectric field of GaN/AlGaN interface [7], [8], where AlGaN is the electron blocking layer (EBL). Kim et al reported that high power and high conversion efficiency can be realized with AlGaInN LEDs [9]. Filling of localized states formed by the InGaN composition fluctuations was studied by Okamoto et al [10].…”