Carrier dynamics in self-organized quantum dots and their application to long-wavelength sources and detectors

Carrier dynamics in self-organized quantum dots have been studied using tem perature-dependent differential transmission spectroscopy and room temperat ure high-frequency electrical impedance measurements on quantum dot lasers. These results suggest the existence of a long relaxation time (similar to 100ps) for the excited state carriers at higher temperatures with the domin ant scattering mechanism being electron-hole scattering. The long relaxatio n time is exploited to realize far-infrared sources and detectors based on intersubband transitions in quantum dots. Quantum dot detectors with large detectivity (D* = (9-10)x 10(9) cm Hz(1/2)/W) and responsivity (R = 100 mA/ W) have been reported at T = 40 K. A unique unipolar, intersubband quantum dot laser (13.3 mum) has also been reported at T = 283 K, using the long in tersubband relaxation time and the short interband recombination time to ac hieve population inversion between the ground and the excited states. (C) 2 001 Elsevier Science B.V. All rights reserved.