Due to the k-conservation restriction the intrinsic luminescence from the two-dimensional electron gas 2DEG in modulation-doped MD quantum wells QWs of high structural perfection consists of a sharp peak centered around the band gap instead of a step-like emission band extending up to the Fermi edge as expected. Therefore, in such QWs it is not possible to study the density of states as well as the optical processes involving electrons near the Fermi edge directly by means of photoluminescence PL experiments. In order to observe the luminescence involving all occupied electron states below the Fermi edge in the 2DEG, some mechanism has to be introduced to localize photogenerated holes and relax the k-conserving law. Alloy fluctuations may localize the holes in ternary MD QW, but the random character of this localization potential causes some difficulty for reproducible studies.
This article is from 'Organization of the Optical Society of America Photonic Science Topical Meeting Series. Volume 7. Quantum Optoelectronics Held in Salt Lake City, Utah on 11-13 March 1991,' AD-A253823, p108-111.