Physicists Find Novel Use of X-ray Photoelectron Spectroscopy

A novel application of X-ray photoelectron spectroscopy (XPS) is being pioneered by Lancaster University physicists partnering with technology company Kratos Analytical.

Compound semiconductors are becoming more common in modern devices, such computers, and mobile phones, as they can add features and functionality demanded by consumers (Image credit: Lancaster University)

XPS has the potential to become an essential method in the designing and production quality control of compound semiconductor devices such as vertical cavity surface-emitting lasers (VCSELs).

Compound semiconductors are becoming more common in advanced devices, such mobile phones, and computers, as they can incorporate features and functionality requested by consumers.

The international compound semiconductor market was worth $66bn in 2016 and is forecast to be worth $143bn by 2023.

But, despite the significance of elemental composition in compound semiconductors, its accurate determination is still a challenge, particularly in devices where there are a number of different layers.

XPS is used almost exclusively used on surfaces as it has an extremely small penetration depth into the material of only a few atomic layers.

However, by slowly and carefully etching the material in situ in the XPS machine we have shown that the technique can be applied to allow the accurate determination of the elemental composition of compound semiconductor materials with multiple layers of different alloys.

Professor Manus Hayne from Lancaster University’s Department of Physics

The ability to engineer the optical and electronic properties of compound semiconductors, for example in relation to their alloy composition, and grow many layers of varied semiconductors on top of each other (heterostructures), is a vital part of their success.

Professor Hayne’s work with Kratos is an offshoot of his QR-SPLED project, funded via Innovate UK and the Engineering and Physical Sciences Research Council (EPSRC), in the framework of the UK National Quantum Technologies Programme.

The project is evaluating the viability of mass-producing low-cost, single-photon sources in the form of single-photon light emitting diodes (SPLEDs), by taking advantage of the unique properties of semiconductor nanostructures known as self-assembled quantum rings. It follows on from a recent project in which Professor Hayne and collaborators presented novel quantum-ring VCSELs.

Professor Hayne is an international authority on self-assembled GaSb/GaAs quantum rings and their application in devices such as telecoms-wavelength VCSELs.

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