2D Materials on Compound Semiconductors

Atomically-thin, inherently 2D semiconductors offer nano-scale devices with excellent response to light for ultra-low-power applications. Using exfoliated microflakes, devices and simple integrated circuits have been reported, underpinning potential applications in nano-optoelectronics. Exploring new device functionality along with materials scale-up are the next challenges; only recently have researchers started to address the integration of these materials into the compound semiconductor (CS) platform. Fewer than twenty labs world-wide are equipped to "grow" single-monolayer 2D materials using molecular beam epitaxy (MBE) or atomic layer deposition (ALD). Significantly fewer have the ability to address the hybrid 2D/CS heterostructure which provides an opportunity for academic exploration and industrial exploitation. Thus, the newly-established Cardiff MBE facility, the well-equipped Ser-Cymru Laboratory supported by Oxford ALD provide an internationally unique setting for this CASE Studentship.

Project aims and methods: This student will develop, analyse and simulate a select family of 2D materials (MoS2, WS2 and WSe2) integrated into the GaN platform for optoelectronic applications. She/he will learn/develop new methods to include 2D deposition using both ALD (Oxford), simple exfoliation/transfer methods (Cardiff) along with hybrid heterostructures comprised of 2D/(InAl)GaN alloys (MBE) noting that MoS2 is lattice-matched to In0.15Ga0.85N. Analysis of these new heterostructures includes research-to-wafer-scale xray diffraction, photoluminescence, time-resolved-photoluminescence along with Raman, and supported by band structure simulation. The student will also explore opportunities within PHYSX-CMP and ENGIN Materials Network for complimentary characterization methods and collaborations.

Scientific excellence and outcomes: The challenge of producing highly-crystalline 2D layers via ALD on III-V systems is expected to result in scientific breakthroughs including single-monolayer 2D crystals at moderate process temperatures followed by control of the underlying physics in 2D/III-N alloys, interfaces and heterostructures. Anticipated outcomes include the demonstration and analysis appropriate for future scale-up leading to continued Cardiff-Oxford collaborations such as the EPSRC "Adventurous Manufacturing" Proposal (bid-in-progress).