Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors: reply.

We present some comments to the paper "Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors: comment," [Opt. Express22, A1589 (2014)].

Accurate control of chromaticity and spectra by feedback phosphor-coating.

The chromaticity coordinates and spectra of phosphor-converted LEDs are demonstrated to be well controlled in this study. Through the feedback coating method of stacked yellow, green, and red phosphor layers, the color rendering index (CRI), correlated color temperature (CCT), and spectra are determined to match precisely the desired target. In addition, the reabsorption effect is strongly influenced by the order of stacked phosphor layers and the selected excitation wavelength of phosphors. The degree of reabsorption will modify the original spectra and cause a mismatch between the experimental measurement and the simulation based on the linear superposition of blue light and phosphor-emitted light. This feedback coating method offers an easy approach towards optimized spectra, which can offer the highest luminous efficacy of radiation with excellent color-rendering properties.

Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors.

In this study, we report a novel monolithically integrated GaN-based light-emitting diode (LED) with metal-oxide-semiconductor field-effect transistor (MOSFET). Without additionally introducing complicated epitaxial structures for transistors, the MOSFET is directly fabricated on the exposed n-type GaN layer of the LED after dry etching, and serially connected to the LED through standard semiconductor-manufacturing technologies. Such monolithically integrated LED/MOSFET device is able to circumvent undesirable issues that might be faced by other kinds of integration schemes by growing a transistor on an LED or vice versa. For the performances of resulting device, our monolithically integrated LED/MOSFET device exhibits good characteristics in the modulation of gate voltage and good capability of driving injected current, which are essential for the important applications such as smart lighting, interconnection, and optical communication.

Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons.

Enhancement of the external quantum efficiency of a GaN-based vertical-type light emitting diode (VLED) through the coupling of localized surface plasmon (LSP) resonance with the wave-guided mode light is studied. To achieve this experimentally, Ag nanoparticles (NPs), as the LSP resonant source, are drop-casted on the most top layer of waveguide channel, which is composed of hydrothermally synthesized ZnO nanorods capped on the top of GaN-based VLED. Enhanced light-output power and external quantum efficiency are observed, and the amount of enhancement remains steady with the increase of the injected currents. To understand the observations theoretically, the absorption spectra and the electric field distributions of the VLED with and without Ag NPs decorated on ZnO NRs are determined using the finite-difference time-domain (FDTD) method. The results prove that the observation of enhancement of the external quantum efficiency can be attributed to the creation of an extra escape channel for trapped light due to the coupling of the LSP with wave-guided mode light, by which the energy of wave-guided mode light can be transferred to the efficient light scattering center of the LSP.

High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers.

In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed.