Abstract:In this study, we have grown 380-nm ultraviolet light-emitting diodes (UV-LEDs) based on InGaN/AlInGaN multiple quantum well (MQW) structures on free-standing GaN (FS-GaN) substrate by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD), and investigated the relationship between carrier localization degree and FS-GaN. The micro-Raman shift peak mapping image shows low standard deviation (STD), indicating that the UV-LED epi-wafer of low curvature and MQWs of weak quantum-confined Stark effe… Show more
“…Equation 1 provides a low IRN of 1.7%, which is in good agreement with previous reports based on freestanding GaN grown on sapphire substrates. 27 It is well known that the defects, microstructure, and phase separation in MQWs influence the IRN of MQWs. 25,28 Therefore, these results manifest that the crystal quality and interface uniformity of the InGaN/GaN MQW LEDs' epitaxial structure on the freestanding GaN substrate grown using a Si substrate is as good as or superior to those of the conventional InGaN/GaN LEDs using freestanding GaN substrates grown using other foreign materials such as sapphire and GaAs.…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…25,28 Therefore, these results manifest that the crystal quality and interface uniformity of the InGaN/GaN MQW LEDs' epitaxial structure on the freestanding GaN substrate grown using a Si substrate is as good as or superior to those of the conventional InGaN/GaN LEDs using freestanding GaN substrates grown using other foreign materials such as sapphire and GaAs. 27 Cross-sectional STEM images of the InGaN/GaN MQWs of LED structures on sapphire and freestanding GaN wafers grown using Si substrates are illustrated in Figure 3. As shown in Figure 3(a), there are structural defects such as threading dislocations for the InGaN/GaN LED on the sapphire substrate.…”
We demonstrate the first InGaN/GaN blue light emitting diodes (LEDs) on freestanding GaN grown using a Si substrate. Transmission electron microscopy and X-ray diffraction analysis revealed that the InGaN/GaN multi quantum wells (MQWs) on freestanding GaN grown using Si substrates have excellent structural properties suitable for high-performance optical devices. Photoluminescence measurements confirm the high crystal quality of the InGaN/GaN MQWs and remarkable emission wavelength uniformity with a standard deviation of 0.68%. Light−current−voltage characteristics indicate that the InGaN/GaN LEDs on freestanding GaN grown using a Si substrate exhibit a forward voltage of 3.75 V at a current of 20 mA and rectifying characteristics with very low leakage current and high breakdown voltage. Furthermore, they provide stable blue electroluminescence (λ = 460 nm) with a small variation in the emission wavelength of 0.2% over a 2 in. area. The internal quantum efficiency of InGaN/GaN LEDs on freestanding GaN grown using Si substrates is remarkable at ∼80%. Despite using Si substrates as the support, the optoelectronic properties of the InGaN/GaN LEDs are outstanding. We believe that the InGaN/GaN LEDs based on freestanding GaN crystals extracted from Si substrates are promising for the development of GaN-based high-performance devices.
“…Equation 1 provides a low IRN of 1.7%, which is in good agreement with previous reports based on freestanding GaN grown on sapphire substrates. 27 It is well known that the defects, microstructure, and phase separation in MQWs influence the IRN of MQWs. 25,28 Therefore, these results manifest that the crystal quality and interface uniformity of the InGaN/GaN MQW LEDs' epitaxial structure on the freestanding GaN substrate grown using a Si substrate is as good as or superior to those of the conventional InGaN/GaN LEDs using freestanding GaN substrates grown using other foreign materials such as sapphire and GaAs.…”
Section: ■ Results and Discussionmentioning
confidence: 99%
“…25,28 Therefore, these results manifest that the crystal quality and interface uniformity of the InGaN/GaN MQW LEDs' epitaxial structure on the freestanding GaN substrate grown using a Si substrate is as good as or superior to those of the conventional InGaN/GaN LEDs using freestanding GaN substrates grown using other foreign materials such as sapphire and GaAs. 27 Cross-sectional STEM images of the InGaN/GaN MQWs of LED structures on sapphire and freestanding GaN wafers grown using Si substrates are illustrated in Figure 3. As shown in Figure 3(a), there are structural defects such as threading dislocations for the InGaN/GaN LED on the sapphire substrate.…”
We demonstrate the first InGaN/GaN blue light emitting diodes (LEDs) on freestanding GaN grown using a Si substrate. Transmission electron microscopy and X-ray diffraction analysis revealed that the InGaN/GaN multi quantum wells (MQWs) on freestanding GaN grown using Si substrates have excellent structural properties suitable for high-performance optical devices. Photoluminescence measurements confirm the high crystal quality of the InGaN/GaN MQWs and remarkable emission wavelength uniformity with a standard deviation of 0.68%. Light−current−voltage characteristics indicate that the InGaN/GaN LEDs on freestanding GaN grown using a Si substrate exhibit a forward voltage of 3.75 V at a current of 20 mA and rectifying characteristics with very low leakage current and high breakdown voltage. Furthermore, they provide stable blue electroluminescence (λ = 460 nm) with a small variation in the emission wavelength of 0.2% over a 2 in. area. The internal quantum efficiency of InGaN/GaN LEDs on freestanding GaN grown using Si substrates is remarkable at ∼80%. Despite using Si substrates as the support, the optoelectronic properties of the InGaN/GaN LEDs are outstanding. We believe that the InGaN/GaN LEDs based on freestanding GaN crystals extracted from Si substrates are promising for the development of GaN-based high-performance devices.
“…The almost unchanged structural parameters indicate that the 1.0-nm-thick cap layer can effectively protect InGaN QW layer during the following H 2 treatment process. The interface roughness can be calculated by fitting the FWHMs of the XRD satellite peaks using the following equation [ 18 , 37 ]: Fig. 1 a HRXRD ω/2θ scanning curves and simulations of the samples.…”
InGaN/GaN multiple quantum wells (MQWs) were grown with hydrogen treatment at well/barrier upper interface under different temperatures. Hydrogen treatment temperature greatly affects the characteristics of MQWs. Hydrogen treatment conducted at 850 °C improves surface and interface qualities of MQWs, as well as significantly enhances room temperature photoluminescence (PL) intensity. In contrast, the sample with hydrogen treatment at 730 °C shows no improvement, as compared with the reference sample without hydrogen treatment. On the basis of temperature-dependent PL characteristics analysis, it is concluded that hydrogen treatment at 850 °C is more effective in reducing defect-related non-radiative recombination centers in MQWs region, yet has little impact on carrier localization. Hence, hydrogen treatment temperature is crucial to improving the quality of InGaN/GaN MQWs.
“…[144] Since then, more and more research groups and companies are interested in research on LEDs on GaN bulk substrates. [145,146] The performance of LEDs grown on GaN bulk substrate has achieved quite remarkable progress in recent years. In 2012, Soraa reported an external quantum efficiency of 68% at 180 A•cm −2 and no current crowding is observed at high current density.…”
Three main technologies for bulk GaN growth, i.e., hydride vapor phase epitaxy (HVPE), Na-flux method, and ammonothermal method, are discussed. We report our recent work in HVPE growth of GaN substrate, including dislocation reduction, strain control, separation, and doping of GaN film. The growth mechanisms of GaN by Na-flux and ammonothermal methods are compared with those of HVPE. The mechanical behaviors of dislocation in bulk GaN are investigated through nano-indentation and high-space resolution surface photo-voltage spectroscopy. In the last part, the progress in growing some devices on GaN substrate by homo-epitaxy is introduced.
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