Seminario ciclo 2023: 'Self-Organised Quantum Dots for Advanced Applications in Optoelectronics'

Resumen:

One of the most important devices in optoelectronics is the semiconductor laser because of its high quantum efficiency; its capabilities and the range of applications that have grown tremendously over recent years. The capability to fabricate novel materials on an atomic scale by using sophisticated epitaxial crystal growth techniques has contributed tremendously to the success of semiconductor quantum well (QW) lasers. The QW laser performances can be improved further by implementing new structures containing quantum dots (QDs). QDs can be fabricated using several techniques including lithography-based technologies. However, the self-organisation process shows great potential for the fabrication of three-dimensional structures, which are formed by the Stranski-Krastanov heteroepitaxy growth mode using lattice-mismatched systems. The advantages of this fabrication technique where the QDs are grown in-situ include a homogeneous surface morphology and prevention of defects. In addition, there are no further processes required such as advanced lithography and chemical etching.

The low cost, high performance and high reliability of the QW laser contributed to its mass production within very few years of its invention. However, theoretical calculations expect that the QD lasers to have superior properties compared to those of conventional QW lasers. These include higher characteristic temperature T0 , lower threshold (Ith) currents and narrower linewidth. In the last few years tremendous progress has been made in improving T0 and Tth of QD lasers. Recently, they have overcome the performance of the best QW lasers in terms for example of threshold current, which is one of the figures of merit of this key device. This implies that the QD lasers could potentially revolutionise the optical electronics industry and make them considerably energy efficient and therefore much more attractive from a commercial perspective. In this talk, I will discuss the properties of self-assembled QDs and the progress in the development of QD lasers.