voltage, high mobility, high luminous efficiency, long service life, and tunable bandgap energy by adjusting the aluminum and indium composition covering from ultraviolet to infrared. However, there are drawbacks for GaN. For example, growing GaN on a sapphire or silicon (111) substrate generates dislocation due to lattice mismatch between the GaN epitaxial layer and the substrate. In addition, the strong chemical bond at the interface makes it difficult to separate the epitaxial layer from the substrate, which limits the ability to apply GaN with excellent properties in various fields. Recently, several studies have sought to overcome these problems by adopting 2D materials between the epitaxial layer and the substrate.Xu and co-workers reported the reduced dislocation density in GaN/graphene/GaN structure using self-organized graphene as a nanomask at high-temperature in hydrogen (H 2 ) ambient with many graphene defects. [1,2] Liu and co-workers also reported that when aluminum nitride was grown on plasma-treated graphene, the dislocation density was reduced compared to when directly grown on sapphire. [3] Hong and co-workers proved that the embedded graphene oxide could be used to improve the heat dissipation in GaN light-emitting diodes. [4,5] In addition, other researchers are making efforts to separate epitaxially grown III−V films from the substrate with the help of the 2D material making the weak chemical bond between the epitaxial layer and the substrate that is transferred to the substrate such as graphene/silicon dioxide, [6] graphene/silicon carbide, [7,8] graphene/ gallium arsenide (GaAs), [9] and boron nitride/sapphire [10] structures. Very recently, Kim and co-workers reported demonstration results using various semiconductors that showed that the polarity of 2D materials and bulk play a crucial role in remote epitaxy. The article also provides the necessary general understanding of single-crystalline growth on 2D-material-coated substrates and subsequent exfoliation. [11] However, the earlyreported graphene-loss issue, particularly in GaN growth in metal-organic chemical vapor deposition (MOCVD), remains unclear and warrants investigation to take advantages of graphene in III−V compound semiconductor growth.Here, we investigated how the decomposition of substrates that support the graphene layer affect the graphene layer by Graphene has been adopted in III−V material growth since it can reduce the threading dislocations and the III−V epilayer can easily be separated from the substrate due to the weak chemical bond. However, depending on the substrate supporting the graphene, some substrates decompose in the III−V material growth environment, which results in the problem that no graphene remains. In this study, the influence of temperature-dependent substrate decomposition on graphene through an annealing process that resembles conventional growth conditions in metal-organic chemical vapor deposition (MOCVD) is investigated. It is also confirmed that trimethylgallium, hydrogen, and ammonia gases d...

We report a color tunable display consisting of two passive-matrix micro-LED array chips. The device has combined vertically stacked blue and green passive-matrix LED array chips sandwiched by a transparent bonding material. We demonstrate that vertically stacked blue and green micro-pixels are independently controllable with operation of four color modes. Moreover, the color of each pixel is tunable in the entire wavelength from the blue to green region (450 nm - 540 nm) by applying pulse-width-modulation bias voltage. This study is meaningful in that a dual color micro-LED array with a vertically stacked subpixel structure is realized.

We introduced a thin nickel (Ni) film onto graphene as a current spreading layer for GaN-based blue and ultraviolet (UV) light emitting diodes (LEDs). The thin Ni film was confirmed to improve the electrical properties of the graphene by reducing the sheet and contact resistances. The advantages of Ni on graphene were more remarkable in UV LEDs, in which the operation voltage was reduced from 13.2 V for graphene alone to 7.1 V. As a result, UV LEDs with Ni on graphene showed a uniform and reliable light emission, at $83% of electroluminescence of indium tin oxide.

Current spreading could be improved by using Ag-mesh-combined graphene sheets due to dramatically reducing the sheet resistance.

We fabricated selectively grown Ga-polar GaN nanorods by optimizing metal organic vapor phase epitaxy (MOVPE) growth parameters using continuous-and pulsed-mode approaches. Nucleation layers were grown using continuous mode with H 2 or N 2 as carrier gas, which resulted in pyramidal or hexagonal shapes, respectively. The growth mechanism of nanorods was further studied for the nucleation layer grown with the H 2 case, in which the pyramidal shape of the nucleation layer was observed to be flattened during the initial step of pulsed-mode growth and then evolved into nanorods by Ga clustering on the top c-plane. #