Near-eye display technology is a rapidly growing field owing to the recent emergence of augmented and mixed reality. Ultrafast response time, high resolution, high luminance, and a dynamic range for outdoor use are all important for non-pixelated, pupil-forming optics. The current mainstream technologies using liquid crystals and organic materials cannot satisfy all these conditions. Thus, finely patterned light-emissive solid-state devices with integrated circuits are often proposed to meet these requirements. In this study, we integrated several advanced technologies to design a prototype microscale light-emitting diode (LED) arrays using quantum dot (QD)-based color conversion. Wafer-scale epilayer transfer and the bond-before-pattern technique were used to directly integrate 5-µm-scale GaN LED arrays on a foreign silicon substrate. Notably, the lithography-level alignment with the bottom wafer opens up the possibility for ultrafast operation with circuit integration. Spectrally pure color conversion and solvent-free QD patterning were also achieved using an elastomeric topographical mask. Self-assembled monolayers were applied to selectively alter the surface wettability for a completely dry process. The final emissive-type LED array integrating QD, GaN, and silicon technology resulted in a 1270 PPI resolution that is far beyond the retinal limit.

Forming metal contact with low contact resistance is essential for the development of electronics based on layered van der Waals materials. ReS2 is a semiconducting transition metal dichalcogenide (TMD) with an MX2 structure similar to that of MoS2. While most TMDs grow parallel to the substrate when synthesized using chemical vapor deposition (CVD), ReS2 tends to orient itself vertically during growth. Such a feature drastically increases the surface area and exposes chemically active edges, making ReS2 an attractive layered material for energy and sensor applications. However, the contact resistances of vertically grown materials are known to be relatively high, compared to those of common 2H-phase TMDs, such as MoS2. Most reported methods for lowering the contact resistance have been focused on exfoliated 2H-phase materials with only a few devices tested, and few works on distorted T-phase materials exist. Moreover, nearly all reported studies have been conducted on only a few devices with mechanically exfoliated fl Most reported methods for lowering the contact resistance have been 2 contacts was modulated by conformally coating a thin tunneling interlayer between the metal and the dendritic ReS2 film. Over a hundred devices were tested, and contact resistances were extracted for large-scale statistical analysis. Importantly, we compared various known materials and techniques for lowering contact resistance and found an optimized method. Finally, the reductions in barrier height were directly correlated with exponential reductions in contact resistance and increases in drive-current by almost 2 orders of magnitude.

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To date, many photodetectors exploiting the unique physical properties of transition metal dichalcogenides (TMDs) have been reported. While it is relatively simple to make a new device, optimizing the device’s...