Review—Defect-Tolerant Luminescent Properties of Low InN Mole Fraction In_xGa_1-xN Quantum Wells under the Presence of Polarization Fields

Abstract

Different from the case of GaN or AlGaN alloys, the near-band-edge (NBE) emission of quantum wells (QWs) and even epilayers of InxGa1-xN alloys of low InN mole fractions (x) exhibits high quantum-efficiency (QE) against the presence of threading dislocations (TDs) as high as 109 cm−2. Accordingly InxGa1-xN alloys are exclusively used as an active region of green to ultraviolet light-emitting diodes (LEDs) and laser diodes, as well as the heart of white LEDs. Here, current understandings on the emission mechanisms of InxGa1-xN QWs, especially the defect-tolerant emission probability of localized excitons, are reviewed. There exist three disadvantages in obtaining high QE, namely a high density of TDs that cause the nonradiative recombination, kinetic immiscibility of In-containing alloys that introduces high-concentration Shockley-Read-Hall nonradiative recombination centers (NRCs) consisting of vacancy complexes, and high internal electric-fields across the QWs induced by the polarization discontinuities at heterointerfaces along the c-axis, which decrease the radiative recombination rate. The use of InxGa1-xN alloys of low x overcomes such disadvantages with the aid of In-originated localization effects that prevent excitons from trapping by TDs or NRCs. Simultaneous observation of short diffusion length and sufficiently long nonradiative recombination lifetime at room temperature indicates strong localization of holes or excitons.

Photoionization cross section ratio of nitrogen-site carbon in GaN under sub-bandgap-light irradiation determined by isothermal capacitance transient spectroscopy

“…It was confirmed that the H1 trap in the depletion layer were completely filled by holes under application of U , P 24) i.e., the H1 traps change to the hole-occupied state from the p + -n junction to the deep region (>1 μm), despite the hole diffusion length in n-type GaN of 10 1 to 10 2 nm [35][36][37] because the electron capture cross section of the H1 trap ( -10 22 to -10 21 cm 2 24,38,39) ) is sufficiently smaller than the hole capture cross section ( -10 14 to -10 13 cm 2 24,38,39) ). In sub-E g -light ICTS, the relationship between ÑT and N T is expressed as:…”

Strain-Induced Valence Band Splitting Enabling Above-Bandgap Exciton Luminescence in Epitaxial Mg3N2 Thin Films

“…11,12 Similarly, while other III-nitride semiconductors like AlN, InN, and their alloys, alongside rare-earth active luminescent materials, have been explored extensively in various optoelectronic devices, 13−15 they often fall short in terms of luminescence efficiency. 16 In the oxide class of materials, ZnO has a nearly comparable bandgap (∼3.37 eV) as GaN (∼3.4 eV), but a higher E b of ∼60 meV 10 presents itself as an alternative WBG semiconductor with enhanced luminescence efficiency. Nevertheless, the challenge persists in achieving high-quality p-type ZnO, 17 thereby limiting its applications and driving the search for superior alternative materials.…”

“…Wide-bandgap (WBG) semiconductors have garnered significant interest owing to their diverse functionalities and widespread technological applications in high-power electronics, light-emitting diodes, − solid-state semiconducting lasers, transducers, , and as host materials for single-photon emitters . A critical characteristic of WBG semiconducting materials is their exciton binding energy (BE) (E b ), which plays a pivotal role in determining their luminescence efficiency. , Gallium nitride (GaN), a ubiquitous and industrially vital LED material, exhibits a modest E b of only 26 meV, limiting its luminescence efficiency. , Similarly, while other III-nitride semiconductors like AlN, InN, and their alloys, alongside rare-earth active luminescent materials, have been explored extensively in various optoelectronic devices, − they often fall short in terms of luminescence efficiency . In the oxide class of materials, ZnO has a nearly comparable bandgap (∼3.37 eV) as GaN (∼3.4 eV), but a higher E b of ∼60 meV presents itself as an alternative WBG semiconductor with enhanced luminescence efficiency.…”

Impacts of Si-doping on vacancy complex formation and their influences on deep ultraviolet luminescence dynamics in AlxGa1−xN films and multiple quantum wells grown by metalorganic vapor phase epitaxy

“…[57][58][59][64][65][66] To explain these ameliorative Si-doping effects in the wells or barriers, plenty of models have been proposed. They are Coulomb screening of F pol , 27,28,88) interface flattening realized by establishing wetting conditions provided by Si, 32,[89][90][91] and the change in the band profiles that gives rise to the proper distribution of electron and hole wavefunctions (Y e and Y , h respectively) in the MQWs. 33,92) Particularly for the above-mentioned Al 0.6 Ga 0.4 N/Al 0.75 Ga 0.25 N MQWs, 87,90) Murotani et al 93) have collected important information written in previous literatures, 86,89,90,94) and thought about the reason for the improved NBE PL efficiency of the proper-amount Si-doped wells, as follows.…”