Chapter 3 - Recent advances in quantum dot optoelectronic devices and future trends

Abstract

Quantum dots are zero-dimensional quantum structures whose carriers are found in three-dimensional potential confinement. The physical properties of quantum dots differ in the density of states as the confinement increases. Electron and hole states could be obtained through a complicated process that considers strong electron and hole coupling and interactions. Therefore, the peculiar optical and electrical characteristics of quantum dot devices are predicted in the chapter. The realization of quantum dots (or boxes) with small enough size to be comparable to the de Broglie wavelength was first made by electron-beam lithography and etching. However, this method yielded limited device performance, mainly because of surface damage and difficulties with postgrowth. Since the Stranski–Krastanow growth mode was rediscovered, successful fabrication of quantum dot device structures has been achieved. The chapter demonstrates quantum dot optoelectronic devices—such as quantum dot infrared photodetectors and quantum dot lasers—based on self-assembling quantum dots. Quantum dot lasers could demonstrate thresholdless operation, temperature-insensitive threshold current, and high-speed laser modulation. In addition, highly strained self-assembled quantum dots can be used to obtain 1.3-μm laser diodes on a gallium arsenide (GaAs) substrate for optical-communications applications.