Development of blue-light GaN based micro light-emitting diodes using ion implantation technology.

This study fabricated 10 μm chip size μLEDs of blue-light GaN based epilayers structure with different mesa processes using dry etching and ion implantation technology. Two ion sources, As and Ar, were applied to implant into the LED structure to achieve material isolation and avoid defects on the mesa sidewall caused by the plasma process. Excellent turn-on behavior was obtained in both ion-implanted samples, which also exhibited lower leakage current compared to the sample fabricated by the dry etching process.

Effects of Substrate Temperature on Optical, Structural, and Surface Properties of Metal-Organic Vapor Phase Epitaxy-Grown MgZnO Films.

MgZnO possesses a tunable bandgap and can be prepared at relatively low temperatures, making it suitable for developing optoelectronic devices. MgZnO (~0.1) films were grown on sapphire by metal-organic vapor phase epitaxy under different substrate-growth temperatures of 350-650 °C and studied by multiple characterization technologies like X-ray diffraction (XRD), spectroscopic ellipsometry (SE), Raman scattering, extended X-ray absorption fine structure (EXAFS), and first-principle calculations.

Performance comparison of flip-chip blue-light microLEDs with various passivation.

In this study, arrays of μLEDs in four different sizes (5 × 5 μm, 10 × 10 μm, 25 × 25 μm, 50 × 50 μm) were fabricated using a flip-chip bonding process. Two passivation processes were investigated with one involving a single layer of SiO deposited using plasma-enhanced chemical vapor deposition (PECVD) and the other incorporating AlO deposited by atomic layer deposition (ALD) beneath the SiO layer. Owing to superior coverage and protection, the double-layers passivation process resulted in a three-order lower leakage current of μLEDs in the 5 μm chip-sized μLED arrays.

The Enhanced Performance of Oxide Thin-Film Transistors Fabricated by a Two-Step Deposition Pressure Process.

It is usually difficult to realize high mobility together with a low threshold voltage and good stability for amorphous oxide thin-film transistors (TFTs). In addition, a low fabrication temperature is preferred in terms of enhancing compatibility with the back end of line of the device. In this study, α-IGZO TFTs were prepared by high-power impulse magnetron sputtering (HiPIMS) at room temperature.

Internal moisture barrier layer for improving high-humidity reliability of miniature light emitting diode die without encapsulation.

Atomic layer deposited AlO films are incorporated into miniature light emitting diodes (mini-LEDs) as an internal moisture barrier layer. The experimental results show that the water vapor transmission rate reaches ≤10g/m/day when the AlO thickness is ≥40 nm. The mini-LED with a 40 nm-thick AlO layer shows negligible degradation after 1000 h of 85°C/85% relative humidity testing, whereas the device without an AlO layer fails after only 500 h due to delamination occurring at the GaN surface.

Improved electrical properties of micro light-emitting diode displays by ion implantation technology.

Generally, the inductively coupled plasma-reactive ion etching (ICP-RIE) mesa technology was used to remove p-GaN/MQWs and expose n-GaN for electrical contact in a fabricated micro light-emitting diode (μLED). In this process, the exposed sidewalls were significantly damaged which result in small-sized μLED presenting a strong size-dependent influence. Lower emission intensity was observed in the μLED chip, which can be attributed to the effect of sidewall defect during etch processing.

Sidewall geometric effect on the performance of AlGaN-based deep-ultraviolet light-emitting diodes.

In this study, deep-ultraviolet light-emitting diodes (DUV LEDs) with different chip sidewall geometries (CSGs) are investigated. The structure had two types of chip sidewall designs that combined DUV LEDs with the same p-GaN thickness. By comparing the differences of the characteristics such as the external quantum efficiency droops, light output power, light extraction efficiency (LEE), and junction temperature of these DUV LEDs, the self-heated effect and light-tracing simulation results have been clearly demonstrated to explain the inclined sidewalls that provide more possibility pathway for photons escape to increase the LEE of LEDs; thus, the DUV LEDs with the CSG presented improved performance.

Growth of GaN Thin Films Using Plasma Enhanced Atomic Layer Deposition: Effect of Ammonia-Containing Plasma Power on Residual Oxygen Capture.

In recent years, the application of (In, Al, Ga)N materials in photovoltaic devices has attracted much attention. Like InGaN, it is a direct band gap material with high absorption at the band edge, suitable for high efficiency photovoltaic devices. Nonetheless, it is important to deposit high-quality GaN material as a foundation.

Crystallinity Effect on Electrical Properties of PEALD-HfO Thin Films Prepared by Different Substrate Temperatures.

Hafnium oxide (HfO) thin film has remarkable physical and chemical properties, which makes it useful for a variety of applications. In this work, HfO films were prepared on silicon through plasma enhanced atomic layer deposition (PEALD) at various substrate temperatures. The growth per cycle, structural, morphology and crystalline properties of HfO films were measured by spectroscopic ellipsometer, grazing-incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR), field-emission scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy.

A Review on Gallium Oxide Materials from Solution Processes.

Gallium oxide (GaO) materials can be fabricated via various methods or processes. It is often mentioned that it possesses different polymorphs (α-, β-, γ-, δ- and ε-GaO) and excellent physical and chemical properties. The basic properties, crystalline structure, band gap, density of states, and other properties of GaO will be discussed in this article.

Thermal behavior of AlGaN-based deep-UV LEDs.

This study utilized thin p-GaN, indium tin oxide (ITO), and a reflective passivation layer (RPL) to improve the performance of deep ultra-violet light-emitting diodes (DUV-LEDs). RPL reflectors, which comprise HfO/SiO stacks of different thickness to maintain high reflectance, were deposited on the DUV-LEDs with 40 nm-thick p-GaN and 12 nm-thick ITO thin films. Although the thin p-GaN and ITO films affect the operation voltage of DUV-LEDs, the highly reflective RPL structure improved the WPE and light extraction efficiency (LEE) of the DUV-LEDs, yielding the best WPE and LEE of 2.

Role of Ambient Hydrogen in HiPIMS-ITO Film during Annealing Process in a Large Temperature Range.

Indium tin oxide (ITO) thin films were prepared by high power impulse magnetron sputtering (HiPIMS) and annealed in hydrogen-containing forming gas to reduce the film resistivity. The film resistivity reduces by nearly an order of magnitude from 5.6 × 10 Ω·cm for the as-deposited film to the lowest value of 6.

Compact GaO Thin Films Deposited by Plasma Enhanced Atomic Layer Deposition at Low Temperature.

Amorphous Gallium oxide (GaO) thin films were grown by plasma-enhanced atomic layer deposition using O plasma as reactant and trimethylgallium as a gallium source. The growth rate of the GaO films was about 0.6 Å/cycle and was acquired at a temperature ranging from 80 to 250 °C.

Improved Characteristics of CdSe/CdS/ZnS Core-Shell Quantum Dots Using an Oleylamine-Modified Process.

CdSe/CdS with ZnS/ZnO shell quantum dots (QDs) are synthesized by a one-pot method with various oleylamine (OLA) contents. The crystal structures of the QDs were analyzed by X-ray diffractometry, which showed ZnS diffraction peaks. It was represented that the ZnS shell was formed on the surface of the CdSe/CdS core.

Study on the effect of size on InGaN red micro-LEDs.

In this research, five sizes (100 × 100, 75 × 75, 50 × 50, 25 × 25, 10 × 10 µm) of InGaN red micro-light emitting diode (LED) dies are produced using laser-based direct writing and maskless technology. It is observed that with increasing injection current, the smaller the size of the micro-LED, the more obvious the blue shift of the emission wavelength. When the injection current is increased from 0.

Incorporation of Au Nanoparticles on ZnO/ZnS Core Shell Nanostructures for UV Light/Hydrogen Gas Dual Sensing Enhancement.

ZnO/ZnS nanocomposite-based nanostructures exhibit dual light and gas sensing capabilities. To further boost the light/dual sensing properties, gold nanoparticles (Au NPs) were incorporated into the core-shell structures. Multiple material characterizations revealed that Au NPs were successfully well spread and decorated on ZnO/ZnS nanostructures.

On the mechanism of carrier recombination in downsized blue micro-LEDs.

The mechanism of carrier recombination in downsized μ-LED chips from 100 × 100 to 10 × 10 μm on emission performance was systemically investigated. All photolithography processes for defining the μ-LED pattern were achieved by using a laser direct writing technique. This maskless technology achieved the glass-mask-free process, which not only can improve the exposure accuracy but also save the development time.

Enhanced external quantum efficiencies of AlGaN-based deep-UV LEDs using reflective passivation layer.

In this study, deep ultraviolet light-emitting diodes (DUV-LEDs) with a reflective passivation layer (RPL) were investigated. The RPL consists of HfO/SiO stacks as distributed Bragg reflectors, which are deposited on two DUV-LEDs with different p-GaN thicknesses. The RPL structure improved the external quantum efficiency droops of the DUV-LEDs with thick and thin p-GaN, thereby increasing their light output power by 18.

Advanced Atomic Layer Deposition Technologies for Micro-LEDs and VCSELs.

In recent years, the process requirements of nano-devices have led to the gradual reduction in the scale of semiconductor devices, and the consequent non-negligible sidewall defects caused by etching. Since plasma-enhanced chemical vapor deposition can no longer provide sufficient step coverage, the characteristics of atomic layer deposition ALD technology are used to solve this problem. ALD utilizes self-limiting interactions between the precursor gas and the substrate surface.

Role of Interfacial Oxide in the Preferred Orientation of GaO on Si for Deep Ultraviolet Photodetectors.

It is generally known that a layer of amorphous silicon oxide (SiO) naturally exists on the surface of silicon, resulting in the growth of gallium oxide (GaO) that is no longer affected by substrate crystallinity during sputtering. This work highlights the formation energy between the native amorphous nano-oxide film formed on the Si substrate and monoclinic β-GaO dominating the preferred orientation prepared for deep ultraviolet photodetectors. The latter were deposited on p-type silicon (-Si) with (111) orientation using radio frequency sputtering at 600 °C and post rapid thermal annealing (RTA).

The Effect of Annealing Ambience on the Material and Photodetector Characteristics of Sputtered ZnGaO Films.

Spinel ZnGaO films were grown on c-plane sapphire substrates at the substrate temperature of 400 °C by radio-frequency magnetron sputtering. Post thermal annealing was employed at the annealing temperature of 700 °C in order to enhance their crystal quality. The effect of thermal annealing on the microstructural and optoelectronic properties of ZnGaO films was systematically investigated in various ambiences, such as air, nitrogen, and oxygen.