SiGe based Optoelectronics

The field of this proposal is that of SiGe based optoelectronic devices. Though Si and Ge are now and will remain in the immediate future the most used materials for electronic devices, group IV optical emitters that can rival those made of III-V semiconductors have yet to be realised as commercial devices. If this was achieved it would represent a giant leap forward in technology, as such devices could be easily interfaced with the existing CMOS technology. This would mean the integration on the same chip of both the optical emitter and the logic circuit that drives the device. Undoubtedly a novel development that promises a high return from the global economy.It is worth mentioning that this work fits in the themes of the EPSRC ICT programme Grand challenges in Silicon Technology , in particular GC1 Novel devices and processes using silicon-based technologies , GC2 Modelling and simulation for silicon-based technologies and GC3 Characterisation for silicon-based technologies .This proposal, designed around a research project for a PhD student, describes a combined experimental and modelling approach to designing novel SiGe structures for optoelectronic applications. This work will be performed in collaboration with the University of Roma 3 in Italy, where test structures will be prepared, and a scientific software company, Accelrys Ltd, which is interested in the commercial exploitation of the software developed for this project. The work in Manchester will be predominantly simulations with some assessment work of the semiconductor materials and structures produced in Rome in order to test the viability of the modelling work.The novel modelling tools developed by the applicants will provide an essential tool to solving a wide range of problems in Si optoelectronics that have so far hampered worldwide efforts to transforming what appears to be fundamentally possible into a real device. Silicon, Germanium and their alloys are well known indirect bandgap materials. Computer design of strain engineering of SiGe layers will make possible to understand the paradigm behind the generatation of direct bandgap in real devices. Despite recent efforts Si integrated heteropolar optical devices in the near infrared have not yet been experimentally successfull. In first instance we intend to understand if the limitations are purely practical or fundamental.More important, and a crucial aspect of this proposal, is that a detailed knowledge of the band alignment at the heterointerface will contribute to the current global effort in generating unipolar devices such as Quantum Cascade Lasers operating in the THz regionThe significance of this work is duplex: On one hand the modelling techniques developed will represent a major step towards predictive modelling of large scale simulations of Semiconductors, with implications extending to compound semiconductors and nanostructures. In view of which we have established the commercial collaboration with Accelrys Ltd. On the other hand the impact of the modelling techniques on the current experimental effort could ultimately provide the key to revolutionary SiGe based laser emitters.