Integrated Epitaxical and Colloidal Nanostructure - Introduction

  In the past dozen or so years two classes of quantum dots, the semiconductor self-assembled quantum dots (SAQD) on a crystalline substrate such as InAs/GaAs (figure 1), Ge/Si, etc. [1,2] and the semiconductor nanocrystal quantum dots (NCQDs) such as CdSe, InAs in solution (figure 2) [3,4], have emerged as two independent and dominant classes of quantum structures with considerable potential for advancing nanotechnologies. Some of these properties, largely for the epitaxical quantum dots, have been well optimized and exploited to realize advanced devices such as lasers [5,6], near to long wavelength infra-red detectors [7], solid state amplifiers, resonant tunneling diodes, etc.[2]. By contrast, the strength and continuing predominant study and use of the NCQDs, overwhelmingly II-VI, is in solution environments, such as in biological luminescent labeling[8]. It is natural then to ponder the potential of new phenomena and applications that would follow from the integration of these two fields. This is particularly so if the already sophisticated III-V epitaxical semiconductor based optoelectronic communication technology developed for the 0.98µm to 1.5µm regime could be exploited. Towards this end the canonical system to be examined is integration of InAs based nanocrystal and the InAs/GaAs based epitaxical nanostructure.

Our current studies are focused on two pathways for the integration of colloidal and epitaxial nanostructures: 1. epitaxical overgrowth on chemically synthesized NCQDs and the buried structure (figure 3) 2. NCQDs adsorbed on epitaxical nanostructure (figure 4), their structural nature and the communication between the NCQDs and underlying epitaxical nanostructure.