Recently, there are many breakthroughs of display in the high resolution and vivid colors for applications in virtual/augmented reality. In this study, we have successfully developed a ...<inline-formula> <tex-math notation="LaTeX">64 \times 32 </tex-math></inline-formula> array inline structure of a micro-LED (<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LED) display by metal bonding an LED array with a glass circuit for connecting a passive matrix IC driver. The dimension of each <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LED was <inline-formula> <tex-math notation="LaTeX">100\,\,\mu \text{m}\,\,\times 100\,\,\mu \text{m} </tex-math></inline-formula>. After bonding, the optoelectronic characteristics were measured to evaluate the best process. By the circuit fabricated on glass and by using a bonding design, we were able to increase the usage ratio of the epitaxy layer and reduce the cost of the <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LED display. Au-In metal bonding demonstrated an excellent bonding result that can withstand a shear force up to 12.58 kg after being reinforced with UV glue. The output power of the display was 61 mW under 120 mA (@1.9 V) current injection to the whole display and the wall plug efficiency is 26.75%.
Abstract
In this paper, thin film AlGaInP LED chips with a 50 μm thick composite metal substrate (Copper-Invar-Copper; CIC) were obtained by the wet etching process. The pattern of the substrate was ...done by the backside of the AlGaInP LED/CIC. There was no delamination or cracking phenomenon of the LED epilayer which often occurs by laser or mechanical dicing. The chip area was 1140 μm × 1140 μm and the channel length was 360 μm. The structure of the CIC substrate was a sandwich structure and consisted of Cu as the top and bottom layers, with a thickness of 10 μm, respectively. The middle layer was Invar with a 30% to 70% ratio of Ni and Fe and a total thickness of 30 μm. The chip pattern was successfully obtained by the wet etching process. Concerning the device performance after etching, high-performance LED/CIC chips were obtained. They had a low leakage current, high output power and a low red shift phenomenon as operated at a high injected current. After the development and fabrication of the copper-based composite substrate for N-side up thin-film AlGaInP LED/CIC chips could be diced by wet etching. The superiority of wet etching process for the AlGaInP LED/CIC chips is over that of chips obtained by mechanical or laser dicing.
The Diagram of Feedback Regimes Revisited Donati, S.; Horng, R-H
IEEE journal of selected topics in quantum electronics,
07/2013, Letnik:
19, Številka:
4
Journal Article
Recenzirano
We revisit the well-known Tkach and Chraplyvy (T-C) diagram of feedback regimes in semiconductor lasers. Our aim is twofold: first, extending the classification of feedback effects in the T-C diagram ...to short and long external cavities, and to coherent and incoherent interactions; second and more important, identifying in the diagram feedback phenomena that have been meanwhile studied and developed to noteworthy applications, namely, self-mixing, period-1 and multiperiodicity, intermittency and chaos. We complement the feedback diagram with application regions, so as to describe not only feedback effects detrimental to a laser used as the transmitter of an optical link, but also feedback effects in the weak and strong regime of interaction, developed into applications for instrumentation and communications in recent years.
A single-crystalline ZnGa2O4 epilayer was successfully grown on a c-plane (0001) sapphire substrate through metalorganic chemical vapor deposition. A metal-semiconductor-metal Schottky ...deep-ultraviolet (DUV) photodetector based on a ZnGa2O4 thin film was fabricated through a simple process of E-gun evaporation and thermal annealing. At a bias of 10 V, the ZnGa2O4 photodetectors exhibited excellent performance characteristics such as an extremely low dark current (0.86 pA), a responsivity of 0.46 A/W under 230-nm DUV, a high photo/dark current ratio (up to 4.68 × 104), a sharp cutoff wavelength of approximately 270 nm, and short rise and fall times of 0.96 and 0.34 s. The photogenerated holes trapped in the Schottky barrier and the shrinking of the depletion region under DUV illumination enabled high DUV/visible rejection ratio (3–4 orders with a 20-V bias). Therefore, the Fowler–Nordheim field tunneling emission functioned as the main electron transport mechanism under DUV illumination and improved the photoelectric characteristics of the epilayer.
•High deep-ultraviolet/visible rejection PD based on a ZnGa2O4 epilayer has been fabricated using the Schottky MSM structure.•Dark current for the DUV PD was about 0.86 pA at a bias of ±10 V which was extremely low as compared with those other DUVs.•Under 230-nm DUV (62.5 μW/cm2) illumination, the photocurrent was 4.04 × 10−8 A at a bias of ±10 V.•On/off ratio of the ZnGa2O4 DUV photodetector reached approximately 4–5 orders of magnitude.
In this study, thin-film blue-light micro-light-emitting diodes (μLEDs) were successfully fabricated by laser lift-off technique, which had an emission region of only 10 μm × 10 μm. Additionally, a ...texturing treatment was applied to the top undoped GaN surface. The texturing time was optimized to prevent a total reflective effect and further enhance the light extraction efficiency. As a result, the emission output power (@ 30 mA) and EQE max of the μLED textured for 2 minutes exhibited 1.35 times and 1.64 times higher values as compared with those of μLED with a sapphire substrate, respectively.
The fabrication process and light extraction efficiency of AlGaInP-based flip-chip micro- light-emitting diode (<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-LED) array ...chips are improved by employing a wafer-bonding process, patterned metal contact, and sidewall passivation layers. The epilayers with indium tin oxide (ITO) can be successfully transferred from the GaAs substrate to the sapphire substrate and bound. Three types of patterned n-metal are employed in the <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-LED as a self-aligning mask and light reflection layer, where the n-GaAs layer can be partially removed by the wet etching process. The dry etching process of MESA has been optimized by applying the BCl 3 gas in the inductively coupled plasma (ICP) system, which can suppress the etching rate of the sidewall and improve the etching depth uniformity. Consequently, the leakage current of the <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-LED array chip is decreased from 85 to 7 nA under the bias of −5 V. Moreover, three configurations of the metal contact/n-GaAs structures with Omnidirectional reflector (ODR) have been designed to reduce the emission light absorption, passivating the sidewall of MESA, and enhance the output power. Finally, the 0.52-in red <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-LED array with a chip size of <inline-formula> <tex-math notation="LaTeX">100\,\,\mu \text{m}\,\,\times 100\,\,\mu \text{m} </tex-math></inline-formula> and resolution of 138 pixels/in is realized when bonded with the drive IC. Consequently, the <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>-LED array chips with ODR and patterned contact show the highest external quantum efficiency of 51.1% and relative output power enhancement of 441% compared to the chip with SiO 2 passivation layer and nonpatterned n-metal contact.
•Deep ultra-violate (DUV) photodetectors (PDs) fabricated by ZnGa2O4 thin film have been studied.•Accelerating life test (ALT) has been examined for UVC PDs.•The reliability issue is caused by the ...surface water adsorption and ozone compensation.•Al2O3 passivation layer was used to protect the device surface from damage by the atmosphere.
Deep ultra-violate (DUV) photodetectors (PDs) fabricated by ZnGa2O4 thin film with back-to-back Schottky type metal–semiconductor-metal (MSM) structure have been studied and presented a superior performance. To further discuss the reliability of DUV device should be the pivot for the DUV application. We were using an accelerating life test (ALT) for UVC PDs by applied in monitoring sterilization light sources during this research. After ALT for one week, the device showed low reliability with a varying current level, and the change of response time and rejection ratio are enormous. Following the XRD and XPS results, we find out that the reliability issue is caused by the surface water adsorption and ozone compensation. Furthermore, the 45-nm-thick Al2O3 passivation layer was deposited by atomic layer deposition (ALD) for isolating the effect of the atmosphere. It resulted in increasing the stability of the current level and reducing the response time for the DUV PDs.
In this study, the epilayer structure of a GaAs solar cell was quickly separated from the GaAs substrate by performing the epitaxial lift-off (ELO) process in hydrofluoric acid (HF) solutions mixed ...with hydrophilic substances, and the epilayer structure was then transferred to a Cu substrate. The lateral etching rate (7.4–14.3μm/min) of the AlAs sacrificial layer, obtained by adding hydrophilic substances – namely acetone (ACE), isopropanol (IPA), and methanol (MA) – to the HF solution was much higher than that obtained using a pure HF solution (3.6μm/min). We attributed the increase in the lateral etching rate to the decrease in both the surface tension of these solutions and the contact angle between the etching-induced bubble and substrate, which enabled efficient venting of bubbles during the ELO process. By contrast, when the HF:ACE solution was used in the ELO process, few solid products were deposited on the sample surface, indicating that there was little obstruction for bubble venting. Therefore, although HF:ACE exhibited the highest surface tension and contact angle among these three solutions, it still resulted in the highest lateral etching rate (14.3μm/min). When the hydrophilic substances were added to HF solution, the cell efficiency was not degraded after the ELO process. Furthermore, the cell device requiring the shortest removal time of the GaAs substrate exhibited the highest efficiency, because of the low etching-induced damage to the GaAs epilayer. Additionally, the GaAs substrate can be rapidly removed and reused via this ELO technique, which is beneficial for photovoltaic applications.
Compared to the lateral etching rate of AlAs sacrificial layer with pure HF solution (3.6μm/min), the higher lateral etching rate of 7.4–14.3μm/min was obtained using these HF-mixture solutions. Display omitted
•The GaAs solar cell was quickly separated from GaAs substrate by epitaxial lift-off.•The HF etchant was mixed with hydrophilic contents to form the etching solution.•HF:ACE mixed etchant possessed the highest lateral etching rate of 14.3μm/min.•The addition of hydrophilic contents leads to the venting of bubbles during ELO.•The cell efficiency was not degraded after ELO process with these mixture solutions.
In this study, we have demonstrated the potential of InGaN-based red micro-LEDs with single quantum well (SQW) structure for visible light communication applications. Our findings indicate the SQW ...sample has a better crystal quality, with high-purity emission, a narrower full width at half maximum, and higher internal quantum efficiency, compared to InGaN red micro-LED with a double quantum wells (DQWs) structure. The InGaN red micro-LED with SQW structure exhibits a higher maximum external quantum efficiency of 5.95% and experiences less blueshift as the current density increases when compared to the DQWs device. Furthermore, the SQW device has a superior modulation bandwidth of 424 MHz with a data transmission rate of 800 Mbit/s at an injection current density of 2000 A/cm
2
. These results demonstrate that InGaN-based SQW red micro-LEDs hold great promise for realizing full-color micro-display and visible light communication applications.
A gas sensor based on a ZnGa
O
(ZGO) thin film grown by metalorganic chemical vapor deposition operated under the different temperature from 25 °C to 300 °C is investigated in this study. This sensor ...shows great sensing properties at 300 °C. The sensitivity of this sensor is 22.21 as exposed to 6.25 ppm of NO and its response time is 57 s. Besides that, the sensitivities are 1.18, 1.27, 1.06, and 1.00 when exposed to NO
(500 ppb), SO
(125 ppm), CO (125 ppm), and CO
(1500 ppm), respectively. These results imply that the ZGO gas sensor not only has high sensitivity, but also has great selectivity for NO gas. Moreover, the obtained results suggest that ZGO sensors are suitable for the internet of things(IOT) applications.
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