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Advances in GaN Crystals and Their Applications
摘要： This special issue looks at the potential applications of GaN-based crystals in both ?elds of nano-electronics and optoelectronics. The contents will focus on the fabrication and characterization of GaN-based thin ?lms and nanostructures. It consists of six papers, indicating the current developments in GaN-related technology for high-ef?ciency sustainable electronic and optoelectronic devices, which include the role of the AlN layer in high-quality AlGaN/GaN heterostructures for advanced high-mobility electronic applications and simulation of GaN-based nanorod high-ef?ciency light-emitting diodes for optoelectronic applications. From the results, one can learn the information and experience available in the advanced fabrication of nanostructured GaN-based crystals for nano-electronic and optoelectronic devices.
关键词： MOSFET,AlN,InN,InGaN,AlGaN,LED,GaN
更新于2025-09-23 15:21:21
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Horizontal GaN nanowires grown on Si (111) substrate: the effect of catalyst migration and coalescence
摘要： Here, we demonstrate the growth of horizontal GaN NWs on silicon (111) by a surface-directed vapour–liquid–solid (SVLS) growth. The influence of the Au/Ni catalysts migration and coalescence on the growth of the NWs has been systematically studied. A 2-D root-like branched NWs were gown spontaneously through catalyst migration. Furthermore, a novel phenomenon that a catalyst particle is embedded in a horizontal NW was observed and attributed the destruction of growth steady state due to the catalysts coalescence. The transmission electron microscopy (TEM) and photoluminescence (PL), cathodoluminescence (CL) measurement demonstrated that the horizontal NWs exhibit single crystalline structures and good optical properties. Our work sheds light on the horizontal NWs growth and should facilitate the development of highly integrated III?V nanodevices on silicon.
关键词： GaN nanowires,silicon substrate,coalescence,catalyst migration,SVLS growth
更新于2025-09-23 15:21:21
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Structural and electrical properties of Pd/p-GaN contacts for GaN-based laser diodes
摘要： In this paper, the properties of Pd-based p-contacts on GaN-based laser diodes are discussed. Pd is often the metal of choice for ohmic contacts on p-GaN. However, for Pd/p-GaN ohmic contacts, nanovoids observed at the metal/semiconductor interface can have a negative impact on reliability and also reproducibility. The authors present a thorough analysis of the microstructure of the Pd/p-GaN interface by x-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). STEM data show that the microvoids at the p-GaN/Pd interface form during rapid thermal annealing. A combination of the following effects is suggested to support the void formation: (1) the differences in thermal expansion coefficients of the materials; (2) excess matrix or impurity atoms in the semiconductor, at the interface, and in the metals, which are released as gases; and (3) the strong antisurfactant effect of Pd on Ga-rich p-GaN surfaces. A slow temperature ramp during contact annealing reduces the formation of voids likely by suppressing the accumulation of gases at the interface. XPS data show that the Ga/N ratio can be reduced by suitable cleaning of the p-GaN surface, which enhances Pd adhesion. As a result, the quality of the contact system is improved by the systematic optimization of the surface cleanliness as well as the annealing parameters, leading to void-free and clean Pd/p-GaN interfaces. The specific contact resistance, extracted from linear transmission line method measurements, is reduced by an order of magnitude to 2 × 10?3 Ω cm2 at 1 mA for the same epitaxial layer stack.
关键词： Pd/p-GaN contacts,STEM,nanovoids,ohmic contacts,rapid thermal annealing,XPS,GaN-based laser diodes
更新于2025-09-23 15:21:01
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Mechanism of leakage current increase in p-GaN gate AlGaN/GaN power devices induced by ON-state gate bias
摘要： An increase in OFF-state leakage current in p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs), induced by ON-state gate bias, was observed and reported in this paper. Higher OFF-state leakage current was observed with higher gate bias voltage and longer bias duration. We propose that the initial increase in OFF-state leakage current and its subsequent decay with time are due to persistent photoconductivity effects in GaN induced by hole injection and electroluminescence during the ON-state gate bias. At room temperature, it took more than 20 s for the increased leakage current to reduce to its equilibrium level in the dark. The related physical mechanisms underlying this phenomenon in the p-GaN gate HEMT structure are also proposed.
关键词： p-GaN gate,AlGaN/GaN HEMTs,persistent photoconductivity,leakage current,electroluminescence
更新于2025-09-23 15:21:01
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Analysis and design of a multi-channel constant current LED driver based on DC current bus distributed power system structure
摘要： In this paper, we have extensively investigated the impact of anode recess on the reverse leakage current, forward voltage (VF), and dynamic characteristics of Au-free AlGaN/GaN Schottky barrier diodes with a gated edge termination (GET-SBDs) on 200-mm silicon substrates. By increasing the number of atomic layer etching (ALE) cycles for anode recessing, we have found that: 1) the reverse leakage current is strongly suppressed due to a better electrostatic control for pinching off the channel in the GET region; a median leakage current of ～1 nA/mm and an ION/IOFF ratio higher than 108 have been achieved in GET-SBDs with six ALE cycles; 2) the forward voltage (～1.3 V) is almost independent of the ALE cycles, taking into account its statistical distribution across the wafers; 3) when the remaining AlGaN barrier starts to be very thin (in the case of six ALE cycles), a spread of the ON-resistance, mainly attributed to the GET region, can occur due to the dif?cult control of the remaining AlGaN thickness and surface quality; and 4) the dynamic forward voltage of GET-SBDs shows a mild dependence on the ALE process in pulsed I–V characterization, and a more ALE-dependent dynamic ON-resistance is observed.
关键词： atomic layer etching (ALE),200-mm,leakage,metal–insulator–semiconductor high-electron mobility transistor (MISHEMT),GET-SBD,diode,AlGaN/GaN
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Small Batch Production and Test of Custom Support Electronics for Infrared LED Scene Projectors
摘要： This letter reports a GaN vertical trench metal–oxide–semiconductor field-effect transistor (MOSFET) with normally-off operation. Selective area regrowth of n+-GaN source layer was performed to avoid plasma etch damage to the p-GaN body contact region. A metal-organic-chemical-vapor-deposition (MOCVD) grown AlN/SiN dielectric stack was employed as the gate “oxide”. This unique process yielded a 0.5-mm2-active-area transistor with threshold voltage of 4.8 V, blocking voltage of 600 V at gate bias of 0 V, and on-resistance of 1.7 Ω at gate bias of 10 V.
关键词： GaN,vertical transistor,MOSFET,power semiconductor devices
更新于2025-09-23 15:21:01
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Improvement in efficiency and luminous power of AlGaN-based D-UV LEDs by using partially graded quantum barriers
摘要： In this article, we have demonstrated a new AlGaN-based D-UV LED (Deep-Ultraviolet Light Emitting Diode) structure and investigated improved electrical output characteristics theoretically. In the new structure, we have used partially graded quantum barriers (PQBs) rather than stepped quantum barrier (SQBs) as setup in conventional LEDs. The simulation results confirm that the usage of PQBs in new D-UV LED structure notably enhances the internal quantum efficiency (IQE), light output power (LOP) or luminous power and enhances power spectral density in the D-UV region. The reason behind this improvement is higher potential barrier for carriers in the active region which helps in improving the carrier’s confinement in the quantum wells and favors significant increment in radiative recombination.
关键词： AlGaN,Efficiency,Luminous power,GaN,LED
更新于2025-09-23 15:21:01
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Towards bright and pure single photon emitters at 300 K based on GaN quantum dots on silicon
摘要： Quantum dots (QDs) based on III-nitride semiconductors are promising for single photon emission at non-cryogenic temperatures due to their large exciton binding energies. Here, we demonstrate GaN QD single photon emitters operating at 300 K with g(2)(0) = 0.17 ± 0.08. At this temperature, single photon emission rates up to 106 s?1 are reached while g(2)(0) ≤ 0.5 is maintained. Our results are achieved for GaN QDs embedded in a planar AlN layer grown on silicon, representing a promising pathway for future interlinkage with optical waveguides and cavities. These samples allow exploring the limiting factors to key performance metrics for single photon sources, such as brightness and single photon purity. While high brightness is assured by large exciton binding energies, the single photon purity is mainly affected by the spectral overlap with the biexcitonic emission. Thus, the performance of a GaN QD as a single photon emitter depends on the balance between the emission linewidth and the biexciton binding energy. Small GaN QDs with an emission energy in excess of 4.2 eV are promising candidates for future room temperature applications, since the biexciton binding energy becomes comparable to the average emission linewidth of around 55 meV.
关键词： single photon source,GaN,room temperature,wide bandgap,quantum dot
更新于2025-09-23 15:21:01
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A broadband ultraviolet light source using GaN quantum dots formed on hexagonal truncated pyramid structures
摘要： Broadband ultraviolet (UV) emission has been achieved from the GaN quantum dots grown on different facets of hexagonal truncated pyramidal structures. The GaN-based structures include both semipolar and polar facets, on which the intrinsic piezoelectric fields and the growth rates are different. In addition, a strain is locally suppressed at the boundaries of the truncated pyramid structure. As a result, the emission wavelength of quantum dots on various facets and boundaries becomes quite different, rendering a solid-state broadband UV light source with homogenerous intensity in a wide wavelength range.
关键词： broadband ultraviolet emission,GaN quantum dots,solid-state broadband UV light source,hexagonal truncated pyramid structures
更新于2025-09-23 15:21:01
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Dimensioning a full color LED microdisplay for augmented reality headset in a very bright environment
摘要： This paper focuses on the dimensioning of a very bright full color 10 μm-pitch light-emitting device (LED) microdisplay for avionics application. Starting from the specifications of head-mounted display to be used in an augmented reality optical system, a theoretical approach is proposed that enables predicting the specifications of the main technology building blocks entering into the microdisplay manufacturing process flow. By taking into account various material and technological parameters, kept as realistic as possible, it is possible to assess the feasibility of a very bright LED microdisplay (1 Mcd/m2 full white) and to point out the main limitations. The theoretical specifications are then compared with the technical results obtained so far in the framework of the H2020 Clean Sky “HILICO” project. It shows that 350 000 cd/m2 of white emission may be accessible with the present gallium nitride (GaN)-micro-LED technology provided a color conversion solution with stable external quantum efficiency of 30% is available. Beyond such level of luminance, the inherent limitations of driving circuit (4 V, 15 μA per pixel) commands working with materials enabling higher external quantum efficiency (EQE). In particular, 10-μm-pitch micro-LEDs with electroluminescence EQE of 15% and color conversion EQE approaching 60% are needed, opening the way to future challenging material and technology research developments.
关键词： active matrix,high luminance,microdisplay,GaN,color conversion
更新于2025-09-23 15:21:01