Optical spectroscopy of ultrasmall structures etched from quantum wells

We have studied the photoluminescence and photoexcitation spectra of ultrasmall structures, of approximately 500 Å in dimension, which we refer to as quantum ribbons and quantum disks. These are fabricated from GaAs-AlGaAs quantum wells grown by molecular beam epitaxy and patterned by electron beam lithography. Contrary to our expectation, photoluminescence from these structures is extremely efficient. The excitation spectra of the two types of small structures differ greatly from each other and from that of the as-grown quantum wells. These differences may be a result of the confinement of the carriers in these small structures.