Fabrication of Semiconductor Quantum Dots

Abstract

The fabrication of semiconductor structures with precisely controlled nanomeLer scale compositional variations have given designers of electronic and photonic devices a new degree of freedom in the control of material properties, and have made possible entirely new classes of electronic and photonic devices (Vahala, 1988). The synthesis of quasi zero-dimensional systems, called quantum dots, has been proposed as an even more exciting development because the electronic state space in these structures is discrete as a result of the three dimensional confinement. The benefits of this confinement can only be realized if the dimensions of the structures can be controlled to within very tight tolerances. The necessary control has been achieved in quantum well structures through the application of molecular beam epitaxi techniques. Efforts to synthesize photonic devices from quantum dots have, however, been frustrated by the inability to control the scale of the structures produced by lithographic methods with sufficient precision. It is estimated that the size of a gallium arsenide cluster of 5 nm diameter should be controlled to within 0.5 nm (Vahala, 1988).