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Narrow-line InGaN/GaN green laser diode with high-order distributed-feedback surface grating
摘要： We demonstrate narrow-line green laser emission at 513.85 nm with a linewidth of 31 pm and side-mode suppression ratio of 36.9 dB, operating under continuous-wave injection at room temperature. A high-order (40th) distributed-feedback surface grating fabricated on multimode InGaN-based green laser diodes via a focused ion beam produces resolution-limited, single-mode lasing with an optical power of 14 mW, lasing threshold of 7.27 kA cm?2, and maximum slope efficiency of 0.32 W A?1. Our realization of narrow-line green laser diodes opens a pathway toward efficient optical communications, sensing, and atomic clocks.
关键词： InGaN/GaN,green laser diode,distributed-feedback,narrow-line,surface grating
更新于2025-11-28 14:23:57
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High-quality nanodisk of InGaN/GaN MQWs fabricated by neutral-beam-etching and GaN regrowth: Towards directional micro-LED in top-down structure
摘要： A nanodisk array of blue InGaN/GaN multiple quantum wells was made using neutral beam etching (NBE) followed by GaN regrowth. The NBE-fabricated nanodisk presented a vertical and highly smooth sidewall surface where the InGaN well layers were easily distinguished even with a scanning electron microscope. A high interface quality without any voids or obvious defects was obtained between the nanodisk and the regrown-GaN layer. The nanodisk after regrowth presented a smaller blueshift of photoluminescence emission energy (12 meV) and a substantially higher and almost constant internal quantum efficiency of ~50% over three orders of magnitude of excitation laser power when compared to the nanodisk before regrowth. This study shows that the process of NBE nanodisk etching followed by GaN regrowth represents a promising step forward in the development of truncated cone-shaped directional micro-LEDs with a buried active region in a top-town structure.
关键词： Regrowth,InGaN/GaN MQWs,Directional micro-LED,Nanodisk,Neutral beam etching
更新于2025-09-23 15:21:01
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AIP Conference Proceedings [AIP Publishing 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019) - Bikaner, India (14a??15 October 2019)] 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019) - Effect of polarization field and Auger recombination on internal quantum efficiency of InGaN/GaN blue LED
摘要： InxGa1-x N/GaN blue LEDs faces significant efficiency droop issue. The causes of efficiency droop are Shockley Read Hall recombination (SRH), Auger recombination (AR), carrier delocalization and electron leakage. The SRH, Auger and electron leakage are functions of carrier concentration and temperature. InGaN/GaN superlattice has polarization electric field at interface. In this work we explore effect of polarization electric field on efficiency droop. It is shown that polarization field enhances Auger coefficient resulting in more droop in internal quantum efficiency of blue LED. Thus, for improvement in efficiency, polarization field required to be minimized which requires growth of the material in m- plane instead of c-plane.
关键词： efficiency droop,polarization electric field,Auger recombination,blue LED,InGaN/GaN
更新于2025-09-23 15:21:01
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Thermal and efficiency droop in InGaN/GaN light-emitting diodes: decoupling multiphysics effects using temperature-dependent RF measurements
摘要： Multiphysics processes such as recombination dynamics in the active region, carrier injection and transport, and internal heating may contribute to thermal and efficiency droop in InGaN/GaN light-emitting diodes (LEDs). However, an unambiguous methodology and characterization technique to decouple these processes under electrical injection and determine their individual roles in droop phenomena is lacking. In this work, we investigate thermal and efficiency droop in electrically injected single-quantum-well InGaN/GaN LEDs by decoupling the inherent radiative efficiency, injection efficiency, carrier transport, and thermal effects using a comprehensive rate equation approach and a temperature-dependent pulsed-RF measurement technique. Determination of the inherent recombination rates in the quantum well confirms efficiency droop at high current densities is caused by a combination of strong non-radiative recombination (with temperature dependence consistent with indirect Auger) and saturation of the radiative rate. The overall reduction of efficiency at elevated temperatures (thermal droop) results from carriers shifting from the radiative process to the non-radiative processes. The rate equation approach and temperature-dependent pulsed-RF measurement technique unambiguously gives access to the true recombination dynamics in the QW and is a useful methodology to study efficiency issues in III-nitride LEDs.
关键词： InGaN/GaN light-emitting diodes,carrier dynamics,efficiency droop,pulsed-RF measurement,thermal droop
更新于2025-09-23 15:19:57
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Numerical Investigation of the Impact of ITO, AlInN, Plasmonic GaN and Top Gold Metalization on Semipolar Green EELs
摘要： In this paper, we present the results of a computational analysis of continuous-wave (CW) room-temperature (RT) semipolar InGaN/GaN edge-emitting lasers (EELs) operating in the green spectral region. In our calculations, we focused on the most promising materials and design solutions for the cladding layers, in terms of enhancing optical mode con?nement. The structural modi?cations included optimization of top gold metalization, partial replacement of p-type GaN cladding layers with ITO and introducing low refractive index lattice-matched AlInN or plasmonic GaN regions. Based on our numerical ?ndings, we show that by employing new material modi?cations to green EELs operating at around 540 nm it is possible to decrease their CW RT threshold current densities from over 11 kA/cm2 to less than 7 kA/cm2.
关键词： edge-emitting lasers,InGaN/GaN,numerical simulations,semiconductor devices
更新于2025-09-23 15:19:57
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The electron–hole overlap in the parabolic quantum well light emitting diode is much superior to the rectangular: even to that of a staggered quantum well
摘要： The strong piezoelectric field in the InxGa1?xN/GaN quantum well (QW) LEDs, separates the electrons and holes spatially, which decreases the luminescence. Various shapes and compositions of such QWs are studied to improve the performance. We have studied the transition energy (TE), overlap of electron and hole wave functions, band structures and field distributions of the parabolic QWs (PQW) through the self consistent solutions of Schr?dinger and Poisson equations. The shape of the PQW is varied along with the compositions and dopings. The square of the overlap of electron and hole wave functions i.e. the transition probability (TP) is strikingly increased, compared to the rectangular QW and it is even higher than the symmetrically staggered QW. At a particular current density, for the same TE, the TP of the PQW increases more than two times that of the rectangular QWs. An important feature, desirable for the QW LEDs emerge. The change of the TE with increase in the current density is minimized. A brief theory, computational procedures and the results will be presented in details with suitable discussions.
关键词： Light emitting diodes,J–V characteristics,Transition probability,Transition energy,InGaN/GaN parabolic QWs
更新于2025-09-19 17:15:36
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Implementation of the Taguchi method to optimize p-ohmic contact for InGaN/GaN LEDs
摘要： Low resistance p-ohmic contact on GaN has always been a topic of investigation as the lack of it hinders the fabrication of high efficiency LEDs and laser diodes. The formation of contacts is a two step process: deposition and annealing. The contact resistance strongly depends on the involved parameters of these two processes. A huge number of experiments are to be performed to get the optimized parameter values. However, by using the efficient Taguchi method to design the experiments, the number of tests can be reduced drastically. We implemented this method in the present study and investigated the influence of various parameters on p-contact formation by performing a reduced set of experiments. The normalized contact resistance, transfer length and specific resistivity of the final device are measured to be 0.15 Ω cm, 0.18 μm and 4.52 × 10?5 Ω cm2, respectively. The sensitivity of various parameters on the contact resistance is also investigated.
关键词： Taguchi method,p-ohmic,InGaN/GaN,LED
更新于2025-09-19 17:13:59
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Evaluating the performance of InGaN/GaN multi-quantum-well solar cells operated at elevated temperatures via DC and small-signal AC analysis
摘要： InGaN/GaN multi-quantum-well (MQW) solar cells are investigated with temperature-dependent DC and AC analysis, and the effects of differing QW number and thickness are determined. The carrier transport is shown to be dominated by thermionic emission rather than tunneling at elevated temperature but limited by recombination outside the depletion region. Temperature-dependent AC parameters of the III-N MQW devices in high-level injection are determined through a refined AC circuit model of the device. It is shown that the use of AC small-signal analysis and its ability to extract stored charge in the QWs, the comparison of built-in potential to VOC, and other solar cell critical values allows a device designer insight not possible via DC analysis alone. This critical data suggests that the number of QWs and total depletion volume needs to be matched to the operational temperature of a given high temperature solar cell.
关键词： AC circuit model,multi-quantum-well,solar cells,recombination,VOC,DC and AC analysis,depletion region,built-in potential,InGaN/GaN,thermionic emission,carrier transport,temperature-dependent
更新于2025-09-19 17:13:59
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Large Wavelength Response to Pressure Enabled in InGaN/GaN Microcrystal LEDs with 3D Architectures
摘要： Optical detection of pressure has the advantage of direct and dynamic indication of the pressure distribution with a high spatial resolution. In this study, microcrystal (μ-crystal) light-emitting diodes (LEDs) that can exhibit an unprecedented large wavelength response to pressure are demonstrated. As a key strategy, three-dimensional InGaN/GaN μ-crystals are engineered to have a hollow core and multiple facets with different multiple quantum well (MQW) structures. The unique structure allows pressure-sensitive modulation of the dominantly emitting MQWs, resulting in an anomalously large change of ~50 nm in the ultimate emission wavelength under an external stress of 8 MPa. The underlying mechanism is elucidated via finite-element analysis of the strain development in the μ-crystals and the corresponding piezo-potentials. The results of the study suggest a new capability for dynamic color mapping of the pressure distribution with a high spatial resolution.
关键词： InGaN/GaN microcrystal,micro-LED,optical sensor,wavelength change,pressure sensor
更新于2025-09-19 17:13:59
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Wave-shaped temperature dependence characteristics of the electroluminescence peak energy in a green InGaN-based LED grown on silicon substrate
摘要： This study aimed to investigate temperature dependencies at different injection currents (ICs) of the electroluminescence (EL) spectra from a green InGaN/GaN light-emitting diode (LED) based on multiple quantum wells (MQWs) grown on a Si substrate in a wide range of ICs (0.001–350 mA) and temperatures (6–350 K). The results show that the temperature-changing characteristic of the EL peak energy gradually evolves from an approximately V-shaped temperature dependence into a wave-shaped (three-step blueshift) dependence with increasing IC. Finally, it emerges as an approximately inverted V-shaped temperature dependence. The behavior reflects the fact that the emission related to InGaN is significantly influenced by the changing recombination dynamics of carriers with rising temperature or IC. This is attributed to the presence in the MQW active region of a stronger carrier localization effect across three zones with different average In contents. Moreover, with the decline of the temperature at lower ICs, the temperature behavior of the external quantum efficiency (EQE) value is dominated by the deactivated non-radiative centers. This phenomenon occurs not only in the higher temperature range but also at lower temperatures due to more In-content-induced structural defects, which are confirmed by measurements of the integrated EL intensity as well as the EQE dependence on IC.
关键词： electroluminescence,InGaN/GaN,carrier localization,LED,temperature dependence
更新于2025-09-19 17:13:59