Physical Mechanisms of Self-Organized Formation of Quantum Dots

Abstract

A move towards smaller dimensions is the general trend in modern solid state physics and technology. The size of modern devices is approaching the nanometer scale, for both vertical and lateral dimensions. Applications of ultrathin layers, or quantum wells, for micro- and optoelectronics had gained broad acceptance in the 1980s. The development of heterostructures with still lower dimensionality [quantum wires, where carriers are confined in two directions and move freely in only one direction, and quantum dots (QDs), where carriers are completely confined] took much longer. It became clear that defect-free quantum wire- and especially dot-structures constitute the utmost technological challenge but provide enormous advantages for devices.

The largest class of QDs, which has attracted most attention in basic research and is today finding numerous applications, is that of semiconductor QDs. QDs are ultrasmall insertions of a narrow band gap semiconductor material in a wide band gap semiconductor matrix. At the beginning of the 1990s, a few outstanding discoveries of self-organization phenomena at crystal surfaces for direct fabrication of nanostructures led to a major change of paradigms in semiconductor physics and technology. First, the main focus has been shifted from growing and studying layers (quantum wells) to QDs.