Silicon based QD light sources and lasers

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Realising efficient electrically-pumped lasers based on Si substrates is the transformative step that enables the unification of III-V based communications technology with Si data processing and memory electronics. We will demonstrate that high performance light emitting devices can be fabricated on Si substrates using an approach based on quantum dots (QDs). The successful outcome will provide the basis for cheaper and better Si-based optoelectronic integrated circuits, a key enabler for the Digital Economy, and provide potential solutions for the impending Si CMOS interconnect challenges (where the physical length and energy requirements of the connections between electronic elements limits processing performance). This project is expected to contribute to improving quality of life for consumers and to wealth creation, for example low-cost and increased complexity Si chips for next-generation computers and higher-capacity communication systems.The problems we will address include the very different crystal lattice size, and the different temperature dependence of the lattice size, of Silicon (the basis for most electronics) and the majority of III-V semiconductors (the basis for most light emitting devices) and the low device power consumption requirements for densely integrated components. The research will investigate how to manage the lattice mismatch across the silicon to III-V interface, introduce methods to filter out crystal defects that originate from this region of the device and will use an active layer that is relatively intolerant to any remaining defects generated by this interface. We will investigate how to make devices that require small numbers of electrons and devices that lose a very small number of the photons generated by these electrons using, for example, a wide range of materials such as GaInP for the laser cladding for low optical loss and InGaAsN(Sb) to allow quantum mechanical tunnelling into a small number of lasing states hence minimising electron use. This will make the overall devices very energy efficient which is also necessary to avoid the generation of large amounts of waste heat that is difficult (and energy costly) to dissipate.We will also demonstrate that it is possible to manufacture laser mirrors and waveguides to couple light between the laser and other optical devices, for example amplifiers. We will liase with leading UK based companies that are ideally placed to exploit the immediate outcomes of our work and also interact with other academic groups, where further research is necessary before our advances can be fully exploited. One example is an optical imaging technique that will benefit from increased data acquisition speed, enhanced portability and reduced price of the devices we will produce to allow early diagnosis of, for example, skin cancer or retinal diseases causing blindness.