Quantum Dot Infrared Photodetectors and Focal Plane Arrays
Quantum dots (QDs) are semiconductor nanocrystallites that have dimensions smaller than the de Broglie wavelength of electrons in semiconductors [1,2]. ™ere are generally two size groups of quantum dots obtained from di£erent methods. ™e šrst is colloidal QDs such as CdSe and PbS [3-5]. ™e colloidal QDs can be synthesized in various sizes and forms and can also be combined with conductive polymers. ™e colloidal QDs have a dimension of 3-5nm diameter. ™eir working wavelengths (emission or absorption) are in visible or near infrared (IR) regions. ™e second type is epitaxial QDs such as InAs. Epitaxial QDs are self-assembled nanocrystallites grown by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD) through the Stranski-Krastanow (S-K) growth mode [6,7]. ™e epitaxial QDs have dimensions of usually ∼20-40nm at the base and are 5-8nm high . ™ey work at near infrared (NIR) through far infrared (FIR) regions. In this chapter, we will be focusing on the inter-subband transition in InAs QDs for LWIR optoelectronic devices.