Defect States Induced in GaN-Based Green Light Emitting Diodes by Electron Irradiation

Abstract

The spatial distribution of deep traps in electron irradiated green multi-quantum-well (MQW) GaN/InGaN light emitting diodes was determined by deep level transient spectroscopy with electrical and optical injection. Four major electron traps with levels near Ec-0.2 eV, E c -0.5 eV, E c -0.75 eV, and E c -1.1 eV were observed. The concentration of all electron traps increased with fluence of 6 MeV electrons, correlating with a decrease of the external quantum efficiency (EQE) of LEDs. The concentration of hole traps at E v +0.45 eV also increased with irradiation. The observed EQE changes are partly attributed to trapping of electrons and holes by electron traps in the GaN barriers (E c -0.75 eV, E c -1.1 eV, E v +0.95 eV) and nonradiative recombination in the QWs via electron traps E c -0.5 eV and hole traps E v +0.45 eV. Even traps with levels far from midgap can effectively participate in nonradiative recombination by forming close pairs similar to donor-acceptor pairs if their density is high. This can occur in In-rich fluctuation regions in the QWs, even as the densities averaged over the entire area of QWs as measured by deep level spectroscopy remain relatively low.

Nanosilicon stabilized with ligands: Effect of high‐energy electron beam on luminescent properties

“…To modify the properties of nanopowders, we used a linear electron accelerator with an energy of 7 MeV, the same as in the previous studies 14–16 . The electron mean free path is about 12 mm both in silicon and aluminum.…”

“…To modify the properties of nanopowders, we used a linear electron accelerator with an energy of 7 MeV, the same as in the previous studies. [14][15][16] The electron mean free path is about 12 mm both in silicon and aluminum. If we take E d = 12.9 eV, then the maximum and average energies transferred to silicon atoms are about 3.5 keV and 75 eV, respectively.…”

Study of a GaN/InGaN-based Light Emitting Diode with an Indium Gallium Oxide Current Blocking Layer, Silver Nanoparticles, and a Gallium Oxide Surface Passivation Layer

“…The advantages of GaN/InGaN-based LEDs, e.g., energy conservation, environmental saving, more reliable performance, and remarkably longer lifetime, cause the broad utilization of GaN/InGaN-based LEDs in solid-state lighting, trafficsafety signals, optical communication, and wearable electronics. [1][2][3][4][5][6][7][8] Nevertheless, the external quantum efficiency (EQE), the most important LED factor, is limited due to relatively lower light extraction characteristics at the heterogeneous interface between air and device surface. 9,10 A variety of methods, such as patterned sapphire substrate (PSS), 11 photonic crystal structure, 12 textured sidewalls and surfaces, 13,14 antireflection layer, 15 and back-side reflector 16 have been reported and exploited over the decades to optimize the performance of LEDs.…”

Study of GaN/InGaN Light-Emitting Diodes with Specific Zirconium Oxide (ZrO2) Layers

“…It is known that, due to the progressive development in material civilization and the demand for environmental protection, GaN/ InGaN light-emitting diodes (LEDs) have been extensively studied and extensively applied in full-color outdoor displays, traffic signals, monitor backlight, solid-state lighting, exterior automotive lighting, wearable electronics, visible light communication, and augmented reality owing to good behaviors of a wide direct bandgap and superior thermal stability of GaN material systems. [1][2][3][4][5][6][7][8][9] However, based on the remarkable difference in refractive index between the surrounding air (n = 1) and GaN (n = 2.5), the critical angle of total internal reflection (TIR) is only of 23.5°, which seriously suppresses the total light output attributed to the lower light extraction efficiency (LEE) and the lower external quantum efficiency (EQE) of GaN/InGaN LEDs. [10][11][12][13] Recently, various methods, e.g., pattern sapphire substrate, 14 backside reflector, 15 antireflection layer, 16 textured surfaces and sidewalls, 17,18 microhole array, 19 photonic crystal structure, 20 and hybrid surface structure 21 have been reported to upgrade the performance of GaN/InGaN LEDs.…”