Greatly Enhanced Wall-Plug Efficiency of N-polar AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

Abstract

In this work, we numerically investigate the N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) over the Ga-polar DUV LEDs. The light output power has increased from 7.1 mW of Ga-polar DUV LED to 18.8 mW of N-polar DUV LED at 60 mA, and the wall-plug efficiency (WPE) of N-polar DUV LED is boosted by 104% at 60 mA with the same structure of Ga-polar conventional DUV LED. Furthermore, the higher operation voltage of N-polar DUV LED induced by the large energy difference between the p-type interlayer and the p-GaN hole supplier is noted. To reduce the operation voltage of N-polar DUV LED, the structure with a staircase-like p-type interlayer is proposed. The incorporation of staircase-like aluminum composition p-type interlayer mitigates the large potential barrier for holes injection, and the operation voltage is comparable to the Ga-polar DUV LED. The reduced operation voltage further promotes the WPE of N-polar DUV LEDs. Thus, combined with the promoted electron blocking ability and the mitigated potential barrier for holes of N-polar DUV LED, the greatly enhanced WPE is as high as 4.9% at 60 mA, which is 2.88 times higher than the Ga-polar DUV LED.

High Efficiency Deep Ultraviolet Light-Emitting Diodes With Polarity Inversion of Hole Injection Layer

“…For Sample A, the polarization charges at the interface between p-Al0.5Ga0.5N and p-GaN are positive, which can deplete the holes, accounting for the high hole barrier. The hole injection regions of Sample B and C are Ga-polar, the charges at the interface between p-Al0.5Ga0.5N and p-GaN become negative charges, which enhances hole accumulation and effectively reduces the hole barrier compared with Sample A [14].…”

Enhancing light extraction efficiency of GaN LED by combining complex‐period photonic crystals with doping

“…For example, a high Al molar composition leads to the conversion of transverse electric (TE) polarized light to transverse magnetic (TM) polarized light in AlGaN, 1,6 which inhibits light extraction from the LED surface. In addition, P‐type AlGaN has poor conductivity and low doping efficiency, 7 which limits the hole mobility and further leads to low internal quantum efficiency 6 . These problems have led to the general limitation of the external quantum efficiency of GaN‐based flat‐panel LEDs in these two wavelength bands 3,8 .…”

Enhanced Performance of N-Polar AlGaN-Based Ultraviolet Light-Emitting Diodes With Lattice- Matched AlInGaN Insertion in n-AlGaN Layer

“…Therefore, some studies also focused on efficient p-type doping and energy band modulation [5], [6], [7], [8], [9], [10], [11], [12]. N-polar LEDs naturally exhibit a higher electron-blocking ability and hole injection efficiency than Ga-polar counterparts, which is promising for achieving high-efficiency UV light sources and has been intensively investigated recently [13], [14], [15], [16]. In addition, for a typical lateral UVA LEDs structure, p-type and n-type contact electrodes are placed on the same side, thus introducing a lateral current injection configuration that induces non-uniform current distribution at the edge of the n-side, i.e., the current crowding effect.…”