Study of quantum confined energy levels in self-organized indium(gallium,aluminum)arsenide/(gallium,aluminum)arsenide quantum dots and their application to mid-infrared sources and detectors.

The objective of the present work is to study the growth of self-organized In(Ga,Al)As/GaAs quantum dots grown by molecular beam epitaxy, understand the unique carrier dynamics in this fascinating quasi-zero dimensional system and finally, exploit the favorable dynamics to realize mid-infrared sources and detectors based on intersubband transitions in these dots. The first part of the study involved the improvement of the epitaxial growth technique to produce Stranski-Krastonov quantum dots with very good size uniformity. By using a set of buried In(Ga,Al)As/GaAs stressor dots, highly uniform In(Ga)As/GaAs active region dots were grown, with a very large areal density (∼2 x 1011cm-2). Selective recombination was achieved by engineering the bandgap of the dots. A narrow photoluminescence linewidth of 19 meV was measured at T = 17K. In the second part of the study, the unique carrier dynamics in the quantum dots were exploited to realize mid-infared sources and detectors. A two photon rate equation was solved to verify the possibility of achieving intersubband population inversion and gain. Intersubband spontaneous and stimulated emission centered around 13 mum were observed for the first time in self-organized InGaAs/GaAs quantum dots. The long relaxation times were also used to realize normal incidence mid-infrared (lambda = 4--5 mum) InAs/GaAs quantum dot detectors with the highest detectivity (D* = 3 x 10 9cmHz1/2/W1/2, Vb = 0.2V, T = 100K) and the highest operating temperature (T = 150K) reported so far in any quantum dot system.Ph.D.Applied SciencesCondensed matter physicsElectrical engineeringOpticsPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125822/2/3016896.pd