Graphene nanowalls (GNWs) are wall-like graphene nanosheets that are oriented vertically on a substrate. GNWs have a unique structure and special optoelectronic properties, which enables their use in photodetectors. In this paper, we use plasma-enhanced chemical vapor deposition to directly grow GNWs onto the surface of an n-type lightly doped Si substrate and to optimize the quality of the GNWs by adjusting the growth time and temperature. Furthermore, after the GNWs are lithographically patterned, we use a GNW-Si Schottky structure to develop photodetector arrays which are capable of detecting light from the visible to infrared light spectral range. Throughout the process, GNWs are directly synthesized on a Si substrate without using a catalyst or a transfer step. The process is simple and efficient. Under laser illumination at a wavelength of 792 nm, the highest on/off ratio at zero bias is approximately 105, and the specific detectivity is 7.85 × 106 cm Hz1/2/W. Under a reverse bias of 4 V, the measured responsivity of the detector reaches 1 A/W at room temperature. The device can also produce a light response in the near-infrared band. Upon laser illumination at a wavelength of 1550 nm, the detector shows a responsivity of 12 mA/W at room temperature.

A technique for the in situ growth of patterned graphene by CVD has been achieved directly on insulating substrates at 800 °C. The graphene growth is catalyzed by a Ni−Cu alloy sacrificial layer, which integrates many advantages such as being lithography-free, and almost wrinkle-free, with a high repeatability and rapid growth. The etching method of the metal sacrificial layer is the core of this technique, and the mechanism is analyzed. Graphene has been found to play an important role in accelerating etching speeds. The Ni−Cu alloy exhibits a high catalytic activity, and thus, high-quality graphene can be obtained at a lower temperature. Moreover, the Ni−Cu layer accommodates a limited amount of carbon atoms, which ensures a high monolayer ratio of the graphene. The carbon solid solubility of the alloy is calculated theoretically and used to explain the experimental findings. The method is compatible with the current semiconductor process and is conducive to the industrialization of graphene devices.

Micro-light-emitting diodes (micro-LEDs) are the key to next-generation display technology. However, since the driving circuits are typically composed of Si devices, numerous micro-LED pixels must be transferred from their GaN substrate to bond with the Si field-effect transistors (FETs). This process is called massive transfer, which is arguably the largest obstacle preventing the commercialization of micro-LEDs. We combined GaN devices with emerging graphene transistors and for the first-time designed, fabricated, and measured a monolithic integrated device composed of a GaN micro-LED and a graphene FET connected in series. The p-electrode of the micro-LED was connected to the source of the driving transistor. The FET was used to tune the work current in the micro-LED. Meanwhile, the transparent electrode of the micro-LED was also made of graphene. The operation of the device was demonstrated in room temperature conditions. This research opens the gateway to a new field where other two-dimensional (2D) materials can be used as FET channel materials to further improve transfer properties. The 2D materials can in principle be grown directly onto GaN, which is reproducible and scalable. Also, considering the outstanding properties and versatility of 2D materials, it is possible to envision fully transparent micro-LED displays with transfer-free active matrices (AM), alongside an efficient thermal management solution.

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Currently, applying graphene on GaN based electronic devices requires the troublesome, manual, lengthy, and irreproducible graphene transfer procedures, making it not feasible for real applications. Here, a semiconductor industry compatible...