Pii: 0749-6036(88)90206-6

The investigation of vertical transport in semiconductor heterojunction systems has recently undergone a renaissance due to improved epitaxial techniques in a number of material systems. By usin resonant tunneling, we can perform electronic spectroscopy not only o f the double barrier structure itself, but of any system (with quantized well states) suitably coupled to a resonant tunneling spectrometer. In designing such systems, an important degree of freedom is introduced by utilizing multi-component structures; for example, a GaAs contact AlGaAs barrier InGaAs quantum well. In this structure, the high electron affinity of the quantum well creates a “deep”quantum well, in which we demonstrate that quantum well states can be hidden from transport. Finally, we present results from microfabricated quantum well structures (“quantum dots”) which are sufficiently small in the lateral dimension to introduce size effects. Telegraph noise due to the lateral size of these structures has been observed, and the first indications of lateral quantization in all three dimensions in a semiconductor quantum well are presented.