The advantages of using quantum dots in the active (gain) region of semiconductor lasers were obvious. However, a technique to incorporate these nanostructures in the laser heterostructure was not available. The breakthrough occurred with the invention of self-assembled quantum dots during the growth of strained (mismatched) InGaAs/GaAs heterostructures. This was followed by quantitative characterization of the epitaxial process and optimization of the optical and structural properties of the quantum dots. It was evident that multiple quantum dot layers could be inserted in-situ in laser heterostructures. Subsequently 980nm, 1.3µm and 1.55µm lasers with unprecedented characteristics such as To ® ∞, low chirp, small α-factor and high differential gain were developed and also quantum dot lasers on silicon substrates. More recently, the author’s group demonstrated the first III-nitride visible quantum dot lasers, with the emission wavelength extending to 630nm (red). Use of quantum dots provides more advantages in the III-nitride system than the conventional III-V system. The ability to epitaxially grow blue-, green- and red- emitting quantum dots enables the realization of all-semiconductor white LEDs. Quantum dot light sources are now used in a number of applications. The characteristics of these devices and their applications will be described in this talk.
Pallab Bhattacharya is the Charles M. Vest Distinguished University Professor of Electrical Engineering and Computer Science and the James R. Mellor Professor of Engineering in the Department of Electrical Engineering and Computer Science at the University of Michigan, Ann Arbor. He received the M. Eng. and Ph.D. degrees from the University of Sheffield, UK. Professor Bhattacharya was an Editor of the IEEE Transactions on Electron Devices and is Editor-in-Chief of Journal of Physics D. He has edited Properties of Lattice-Matched and Strained InGaAs (UK: INSPEC, 1993) and Properties of III-V Quantum Wells and Superlattices (UK: INSPEC, 1996). He has also authored the textbook Semiconductor Optoelectronic Devices (Prentice Hall, 2nd edition). His teaching and research interests are in the areas of compound semiconductors, low-dimensional quantum confined systems, nanophotonics, spintronics and optoelectronic integrated circuits. He is currently working on high-speed quantum dot lasers, nitride-based visible quantum dot lasers and LEDs, nanowire heterostructures, cavity quantum electrodynamics and polariton lasers.
Professor Bhattacharya is a member of the National Academy of Engineering and he has been awarded the D. Eng. (honoris causa) degree from the University of Sheffield, U.K. He has also received the John Simon Guggenheim Fellowship, the Heinrich Welker Medal, the IEEE David Sarnoff Award, the IEEE (EDS) Paul Rappaport Award, the IEEE (LEOS) Engineering Achievement Award, the IEEE (Nanotechnology Council) Nanotechnology Pioneer Award, the Optical Society of America (OSA) Nick Holonyak Award, the TMS John Bardeen Award, the SPIE Technical Achievement Award, and the Quantum Devices Award of the International Syposium on Compound Semiconductors. He has also received the S.S. Attwood Award, the Kennedy Family Researcher Excellence Award, and the Distinguished Faculty Achievement Award from the University of Michigan. He is a Fellow of the IEEE, the American Physical Society, the Institute of Physics (UK), the Optical Society of America, and the National Academy of Inventors