Microscopic mapping and spectroscopy of III-nitride semiconductors and devices

The semiconductor spectroscopy group is within the Nanoscience Research Division at Strathclyde University and investigates a wide range of light emitting semiconductor materials using optical and electron-beam techniques. Light emitting devices based on Gallium Nitride (GaN) and related materials are a particular speciality (see http://ssd.phys.strath.ac.uk/index.php/Main_Page). We are partners in a number of major projects, including the “Lighting the Future” programme involving Cambridge, Manchester, Bath and Strathclyde Universities.

Over recent years we have developing ways to combine a number of different microscopic techniques to investigate semiconductor heterostructures and light-emitting diode devices. This project involves experiments that will be performed on our suite of three scanning electron microscopes, providing information on the materials properties at length scales ranging from nanometres to centimetres. Optical information is provided by spatially-resolved cathodoluminescence (CL) [Ref. 1,2], electroluminescence (EL) and photoluminescence (PL) [Ref. 3]. Compositional information can be collected simultaneously with the CL, using X-ray microanalysis [Ref. 4], and details of conductivity and defects can be collected simultaneously with the EL, using electron-beam induced current (EBIC) data. Work with colleagues in the same group (Dr. Trager-Cowan et al.) brings in electron back-scattered diffraction and electron channeling data, providing information of structural properties such as defects and strain [Ref 5].

The combination of these various techniques, with their high spatial resolution, will allow a fuller understanding and optimisation of the properties of the materials and devices. The ability to apply them simultaneously, or in rapid succession, on exactly the same microscopic region of the samples is new and distinctive. The project will involve work to further extend the power of these techniques and their combination. Structures under study will include Indium Gallium Nitride based quantum wells and LEDs, as being developed for highly efficient solid state lighting and other applications.