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 0.1 to 1 mA, the emission wavelength of the 10 × 10 μm
micro-LED is shifted from 617.15 to 576.87 nm. The obvious blue shift is attributed to the stress release and high current density injection. Moreover, the output power density is very similar for smaller chip micro-LEDs at the same injection current density. This behavior is different from AlGaInP micro-LEDs. The sidewall defect is more easily repaired by passivation, which is similar to the behavior of blue micro-LEDs. The results indicate that the red InGaN epilayer structure provides an opportunity to realize the full color LEDs fabricated by GaN-based LEDs.
Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in ...photoelectrochemical (PEC) water splitting applications. Here, we present a simple and efficient strategy for III-V-based photoelectrodes that functionally and spatially decouples the light harvesting component of the device from the electrolysis part that eliminates parasitic light absorption, reduces the cost, and enhances the stability without any compromise in efficiency. The monolithically integrated PEC cell was fabricated by an epitaxial lift-off and transfer of inversely grown InGaP/GaAs to a robust Ni-substrate and the resultant photoanode exhibits an STH efficiency of ~9% with stability ~150 h. Moreover, with the ability to access both sides of the device, we constructed a fully-integrated, unassisted-wireless "artificial leaf" system with an STH efficiency of ~6%. The excellent efficiency and stability achieved herein are attributed to the light harvesting/catalysis decoupling scheme, which concurrently improves the optical, electrical, and electrocatalytic characteristics.
The field of next‐generation microdisplays is flourishing. Relevant display technologies, such as mini‐light emission diodes (mini‐LEDs), micro‐organic light emission diodes (micro‐OLEDs), and ...micro‐light emission diodes (micro‐LEDs) are thus in the urgent stage of development. From this perspective, comprehensive and systematical analyzes are conducted for the aforesaid microdisplay configurations. A holistic view of microdisplay technologies is developed with the corresponding performance metrics, providing a path for miscellaneous scenarios. Among these scenarios, the applications in augmented reality (AR), virtual reality (VR), wearable devices, and head‐up displays (HUD) are currently attracting considerable attention for deeper human‐digital interactions. However, there is a multiplicity of obstacles and challenges hindering such development. Nevertheless, recent advances in microdisplay technologies hold tremendous promise for the paradigms of these applications, taking a leap forward for next‐generation microdisplays. This review presents perspectives, relevant materials, and the technology landscape for such ongoing display technologies, offering guidance on the design of advanced microdisplays.
The demand for augmented reality (AR), virtual reality (VR), wearables, and head‐up display (HUD) technology has fueled the rapid growth of next‐generation microdisplays. Despite their promise, challenges remain. This review analyzes performance metrics across various scenarios and provides valuable materials and technology perspectives for ongoing display technology. Our guidance for advanced microdisplay design aims to overcome obstacles and improve the field.
Abstract
The mechanism of carrier recombination in downsized μ-LED chips from 100 × 100 to 10 × 10 μm
2
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. The multi-functional SiO
2
film as a passivation layer successfully reduced the leakage current density of μ-LED chips compared with the μ-LED chips without passivation layer. As decreasing the chip size to 10 × 10 μm
2
, the smallest chip size exhibited the highest ideality factor, which indicated the main carrier recombination at the high-defect-density zone in μ-LED chip leading to the decreased emission performance. The blue-shift phenomenon in the electroluminescence spectrum with decreasing the μ-LED chip size was due to the carrier screening effect and the band filling effect. The 10 × 10 μm
2
μ-LED chip exhibited high EQE values in the high current density region with a less efficiency droop, and the max-EQE value was 18.8%. The luminance of 96 × 48 μ-LED array with the chip size of 20 × 20 μm
2
exhibited a high value of 516 nits at the voltage of 3 V.
To acquire device-quality TiOx films usually needs high-temperature growth or additional post-thermal treatment. However, both processes make it very difficult to form the p-type TiOx even under ...oxygen-poor growth condition. With the aid of high energy generated by high power impulse magnetron sputtering (HIPIMS), a highly stable p-type TiOx film with good quality can be achieved. In this research, by varying the oxygen flow rate, p-type γ-TiO and n-type TiO2 films were both prepared by HIPIMS. Furthermore, p- and n-type thin film transistors employing γ-TiO and TiO2 as channel layers possess the field-effect carrier mobilities of 0.2 and 0.7 cm2/Vs, while their on/off current ratios are 1.7 × 104 and 2.5 × 105, respectively. The first presented p-type γ-TiO TFT is a major breakthrough for fabricating the TiOx-based p-n combinational devices. Additionally, our work also confirms HIPIMS offers the possibility of growing both p- and n-type conductive oxides, significantly expanding the practical usage of this technique.
The integration of III-V and Si multi-junction solar cells as photovoltaic devices has been studied in order to achieve high photovoltaic conversion efficiency. However, large differences in the ...coefficients of thermal expansion and the lattice parameters of GaAs, Si, and InGaAs have made it difficult to obtain high-efficiency solar cells grown as epilayers on Si and InP substrates. In this paper, two types of devices, including GaInP/GaAs stacked on Si (GaInP/GaAs//Si) and GaInP/GaAs stacked on InGaAs (GaInP/GaAs//InGaAs), are fabricated via mechanical stacking and wire bonding technologies. Mechanically stacked GaInP/GaAs//Si and GaInP/GaAs//InGaAs triple-junction solar cells are prepared via glue bonding. Current-voltage measurements of the two samples are made at room temperature. The short-circuit current densities of the GaInP/GaAs//Si and GaInP/GaAs//InGaAs solar cells are 13.37 and 13.66 mA/cm
, while the open-circuit voltages of these two samples are measured to be 2.71 and 2.52 V, respectively. After bonding the GaInP/GaAs dual-junction with the Si and InGaAs solar cells, the conversion efficiency is relatively improved by 32.6% and 30.9%, respectively, compared to the efficiency of the GaInP/GaAs dual-junction solar cell alone. This study demonstrates the high potential of combining mechanical stacked with wire bonding and ITO films to achieve high conversion efficiency in solar cells with three or more junctions.
Abstract
A single-crystalline ZnGa
2
O
4
epilayer was successfully grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition. This epilayer was used as a ternary oxide ...semiconductor for application in high-performance metal–semiconductor–metal photoconductive deep-ultraviolet (DUV) photodetectors (PDs). At a bias of 5 V, the annealed ZnGa
2
O
4
PDs showed better performance with a considerably low dark current of 1 pA, a responsivity of 86.3 A/W, cut-off wavelength of 280 nm, and a high DUV-to-visible discrimination ratio of approximately 10
7
upon exposure to 230 nm DUV illumination than that of as-grown ZnGa
2
O
4
PDs. The as-grown PDs presented a dark current of 0.5 mA, a responsivity of 2782 A/W at 230 nm, and a photo-to-dark current contrast ratio of approximately one order. The rise time of annealed PDs was 0.5 s, and the relatively quick decay time was 0.7 s. The present results demonstrate that annealing process can reduce the oxygen vacancy defects and be potentially applied in ZnGa
2
O
4
film-based DUV PD devices, which have been rarely reported in previous studies.
Self-heating effect is a major limitation in achieving the full performance potential of high power GaN power devices. In this work, we reported a micro-trench structure fabricated on the silicon ...substrate of an AlGaN/GaN high electron mobility transistor (HEMT) via deep reactive ion etching, which was subsequently filled with high thermal conductive material, copper using the electroplating process. From the current-voltage characteristics, the saturation drain current was improved by approximately 17% with the copper filled micro-trench structure due to efficient heat dissipation. The I
difference between the pulse and DC bias measurement was about 21% at high bias V
due to the self-heating effect. In contrast, the difference was reduced to approximately 8% for the devices with the implementation of the proposed structure. Using Micro-Raman thermometry, we showed that temperature near the drain edge of the channel can be lowered by approximately ~22 °C in a HEMT operating at ~10.6 Wmm
after the implementation of the trench structure. An effective method for the improvement of thermal management to enhance the performance of GaN-on-Silicon HEMTs was demonstrated.
This research studies the performance of n-side up thin-film AlGaInP-based vertical micro-light-emitting diodes (V-<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LEDs) ...with four different chip sizes, <inline-formula> <tex-math notation="LaTeX">100\times100 </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">70\times70 </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">50\times50 </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">25\times 25\,\,\mu \text{m}^{2} </tex-math></inline-formula>, on a <inline-formula> <tex-math notation="LaTeX">50~\mu \text{m} </tex-math></inline-formula> thick composite metal (copper/Invar/copper; CIC) substrate. The LEDs were fabricated to understand the electrical and optical properties of AlGaInP V-<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LEDs as functions of chip sizes. For device performance, the small LEDs provide a larger current density under the same voltage and present smaller forward voltage, a low red-shift phenomenon, and low output power density. For the external quantum efficiency (EQE) of device, larger LEDs exhibit maximum EQE at lower current density as compared to smaller LEDs. The injection of a small current at the same current density obtains the emission image. The obtained data suggest that the smallest V-<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>LEDs exude a sidewall effect that could impact the device performance.
ZnGaO films were grown on c-plane sapphire substrates by metal organic chemical vapor deposition using diethylzinc (DEZn), triethylgallium (TEGa), and oxygen. The flow rate of DEZn was 10–60 sccm, ...and those of TEGa and oxygen were held constant. The ZnGaO film prepared at a DEZn flow rate of 10 sccm adopted a (2̅01)-oriented single-crystalline β-Ga2O3 phase, whereas those prepared at 30–60 sccm exhibited a (111)-oriented single-crystalline ZnGa2O4 phase. On the basis of Hall measurements, ZnGaO films (10 sccm DEZn) possessed very poor electrical properties, which were similar to those of β-Ga2O3. On the other hand, the carrier concentration in ZnGaO films increased from 1.94 × 1014 to 6.72 × 1016 cm–3, and the resistivity decreased from 5730 to 67.9 Ω-cm when increasing the DEZn flow rate from 30 to 60 sccm. According to compositional analyses, the improved electrical properties of ZnGaO films upon increasing DEZn flow rate from 30 to 40 sccm are due to the increasing Zn content, and the enhancement from 50 to 60 sccm could be due to increased C content. Cathodoluminescence results also confirm the ZnGa2O4 structure for ZnGaO films prepared at DEZn flow rates of 30–60 sccm and reveal their use for ultraviolet applications.
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