We use a variety of ab initio (CASTEP) and empirical (IMD) methods for evaluating crystal properties such as strain, piezoelectricity, electronic bandstructure, morphology of layers of group IV, III-V and II-VI semiconductors.
- Empirical force fields - We are experts in the development and use of empirical force fields for Molecular Dynamics and application of these to the study of nanostructures and Graphene.
- Non Linear Piezoelectricity - We are also active in the study of Non Linear Piezoelectricity. Our interest is the development of new material configurations capable of high piezoelectric response, in order to maximize e.g. the voltage produced at the ends of a polar semiconductor Nanowire. Such voltage can be used to convert vibrations into an electric current capable of powering small circuits (Nanogenerators-Piezotronics).
- Light emitting diodes (LEDs) - We also work on control of piezoelectricity in the design of novel InGaN light emitting diodes (LEDs) for solid state lighting sources.
Amongst all material system in the III-V compound semiconductors, InGaAs/InAlAs materials system has the most desirable band structure and transport properties.
With the device size scaling down to few nanometer regime and various epitaxial layer structures being designed, empirical and physical modeling becomes essential to fully characterize the device technological process, analyze circuit performance and understand the underlying physical phenomenon of the device. The two-dimensional (2-D) physical modeling for an in-house fabricated 0.25m gate length with multiple sized gate width InAlAs/InGaAs InP based pHEMT is developed using ATLAS SILVACO to appreciate the underlying device physics of the device, to reproduce the DC and RF device characteristic, and to investigate the correlation of the device physics to the output characteristics.
The optimized linear and nonlinear models which are performed in Advance Design System (ADS) software are used to obtain an LNA circuit design and to analyse the device performance in the frequency range of 0.5GHz to 20 GHz. This research aims to develop models for new transistors and their implementation in the MMIC LNA circuit design using the extensive facilities available at the University of Manchester. The fabricated InP-based pHEMT device is used to design high frequency MMIC LNA particularly for X-band (8 – 12GHz) applications.