The ability to fabricate free standing semiconductor quantum wells
enables the study of excitons and electrons under the textbook condition
of infinite barriers, i. e., the 2-D particle in a box. We have selectively
etched compositionally modulated III-V heterostructures to produce quantum
wells which are confined on both sides by vacuum. The material is
patterned so that the wells are suspended horizontally between vertical
supports. This structure is ideal for probing the local properties
of
solids, e. g., the interaction of quantum confined states with surface
or interface states. The inherent high contrast ratio also allows
the construction of efficient mirrors for lasers. This is of particular
interest in that it allows the fabrication of a Fabry-Perot laser cavity
with a linear dimension on the order of the spontaneous emission
wavelength of the active medium. The satisfaction of this criterion
limits the emission to a single mode and would substantially lower the
emission threshold. We have been able to achieve reproducible well
widths from 80-200 Å with variable spacings from 100 to 2000 Å
without difficulty.