The general trend in modern solid state physics and technology is to make things smaller. The size of key elements in modern devices approaches the nanometer scale, for both vertical and lateral dimensions. Ultrathin layers, or quantum wells, had already gained broad acceptance for applications in micro- and optoelectronics by the 1980s. However, the development of het- erostructures with lower dimensionality (quantum wires, where carriers are confined in two directions and move freely in one, and quantum dots, where carriers are confined in all three directions) took longer. It became clear...