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This paper reports enhanced internal-quantum-efficiency (IQE) in InGaN-based multi-quantum-well (MQW) grown on Si(111) substrate with underlying strained-layer-superlattice (SLS) cladding layer for application in LDs and LEDs. In comparative study between a thick Al0.03Ga0.97N bulk and an Al0.06Ga0.94N/GaN SLS cladding layer, transmission-electron-microscopy (TEM) images reveal that Al0.06Ga0.94N/GaN SLS cladding layer is effective to suppress threading dislocations. A higher IQE has been achieved in sample with underlying Al0.06Ga0.94N/GaN SLS cladding layer, compared to that of Al0.03Ga0.97N bulk cladding layer. IQE of 31.6% has been achieved in sample with underlying Al0.06Ga0.94N/GaN SLS cladding layer when the MQW thickness is reduced to 2 nm.

This paper reports improved optical characteristics of InGaN-based light-emitting-diode (LED) grown on Si(111) substrate by the insertion of an Al0.06Ga0.94N/GaN strained-layer-superlattices (SLS) cladding layer after AlN/GaN multilayer (ML) growth, under the multi-quantum-well (MQW) active layer. The insertion of underlying Al0.06Ga0.94N/GaN SLS cladding layer has shown to improve epitaxial layer quality in x-ray diffraction (XRD) analysis, reduce wavelength peak fluctuations in photoluminescence (PL) surface mapping, and improve optical and electrical characteristics of the LED sample. A 34% increase of light intensity at 50 mA current injection and a narrower wavelength peak have been achieved by the insertion of Al0.06Ga0.94N/GaN SLS cladding layer. LED with underlying Al0.06Ga0.94N/GaN also shows superior current-voltage (I-V) characteristics with operation voltage of 3.2 V at 20 mA and series resistance of 16 Ω.

We report high performance InGaN multiple-quantum well (MQW) light-emitting diodes (LEDs) grown on Si (1 1 1) substrates using metalorganic chemical vapour deposition (MOCVD). A high-temperature thin AlN layer and AlN/GaN multilayers have been used for the growth of a high-quality GaN-based LED structure on Si substrates. Reduction of the high-temperature AlN layer thickness promotes the formation of a tunnel junction at the AlN/Si interface which reduces the LED operating voltage. Optical output power of the LED on Si saturates at a higher injected current density due to higher thermal conductivity of Si than that of a sapphire substrate. At a high injection current, output power of the LED on Si is higher than that of the LED on sapphire. Cross-sectional transmission electron microscopy (TEM) indicates that the active layer of these LEDs consists of a dislocation-free pyramid-shaped (quantum-dot-like) structure. Additionally, the crack-free thin-film LED epilayer region was transferred onto a copper carrier using metal-to-metal bonding and the selective lift-off technique. A LED with high output power, low operating voltage and low series resistance was realized by this technique. Furthermore, optimization of LED on Si by insertion of an Al0.06Ga0.94N/GaN strained-layer superlattice underlayer into the structure exhibits improved internal quantum efficiency (ηiqe) in the MQW, higher optical emission intensity with higher saturation current, lower operation voltage of 3.2 V at 20 mA and a series resistance of 16 Ω, as well as narrower electroluminescence spectra.

We report effect of the insertion of Al0.06Ga0.94N/GaN strained-layer superlattices (SLSs) cladding underlayer to InGaN-based multi-quantum well (MQW) structure grown on Si(111) substrate with AlN/GaN intermediate layer. The Al0.06Ga0.94N/GaN SLS underlayer improves emission wavelength uniformity and shows a narrower emission full-width at half-maximum (FWHM) than that of conventional GaN underlayer. A Gaussian fitting was performed to photoluminescence (PL) spectra to obtain emission wavelength behavior and integrated intensity of the peak energy. A higher MQW internal quantum efficiency (ηiqe) of 29.4% is obtained in sample with Al0.06Ga0.94N/GaN SLS underlayer than that of 20.6% in GaN underlayer. Transmission electron microscopy (TEM) analysis indicates that the Al0.06Ga0.94N/GaN SLS layer abruptly bends threading dislocation lines thus reduces threading dislocation density to the MQW. Reciprocal space mapping (RSM) suggests that compressive strain in the GaN portion of Al0.06Ga0.94N/GaN SLS forces the abrupt inclination of the threading dislocations.

This paper reports growth and material characterization of InGaN-based laser diode (LD) structure grown on Si(111) substrate by metal organic chemical vapor deposition (MOCVD) with a high-temperature-grown thin AlN buffer layer and an AlN/GaN multi-layer (ML) intermediate layers. Two types of LD structures on Si were prepared, (a) with bulk n-and p-type Al0.02Ga0.98N cladding layer, and (b) with SLS n- and p-type Al0.06Ga0.94N/GaN cladding layer. Active layer with 3 periods of In0.10Ga0.90N/In0.03Ga0.97N multi-quantum-well (MQW) is sandwiched between the cladding layers. A standard LD structure (c) with identical MQW grown on GaN(0001) free-standing substrate was also prepared for comparison. Mirrorlike and meltback-etching free surfaces have been achieved for both of the samples grown on Si. High-resolution x-ray diffraction (HRXRD) ω/2θ scan reveals that a good quality of MQW has been achieved for both of the samples grown on Si. Temperature-dependence PL measurement reveals that LD structure grown on Si with SLS cladding layer has higher internal quantum efficiency ηint than that of the sample with bulk cladding layer.