III–V quantum dots for optoelectronic device applications

Quantum dots (QDs) grown by Stranski-Kranstanov method are of current interest for the application of high performance optoelectronic devices due to their unique three dimensional carrier confinement. However, one big limitation for the QD-based devices is the difficulties in predicting and controlling their operating wavelength accurately due to the extremely sensitive selforganized process of dot formation. In this talk, we will demonstrate the growth, fabrication and characterisation of two main optoelectronic devices, namely QD lasers and infrared photodetectors (QDIPs), by metal-organic chemical vapour deposition (MOCVD). Various QD structural design, growth and processing schemes will be also presented for spectral tuning of the lasers and QDIPs, including the approach of selective area epitaxy (SAE), the use of dots-in-a-well (DWELL) structure as well as the postgrowth technique of QD intermixing (QDI). These methods are essential for achieving high quality quantum dot-based devices and photonic integrated circuits. Finally, we will also present some preliminary results on the investigation of employing QDs to form the so-called intermediate band (IB) structure in solar cells to further improve the efficiency of conventional single gap solar cells.