A.F. Ioffe Physicotech. Inst., Acad. of Sci., St. Petersburg, Russia

Fizika i Tekhnika Poluprovodnikov , vol.27, no.7 , Page: 1101-12 , July 1993

Translated in: Semiconductors , vol.27, no.7 , Page: 606-12 , July 1993

Abstract: The low-temperature photoluminescence emitted by quantum wells located at short distances (0-500 AA) from the surface of a structure has been studied. The thickness of the barrier layer, which separates a quantum well from the surface, was reduced by etching. When the barrier thickness was less than 300 AA, a long-wavelength shift (up to 12 meV for a well of 50 AA width) and quenching (down to 1/1000) of the photoluminescence line were observed.The dependences of the long-wavelength shift on the barrier thickness and the well width, and also on the photoexcitation intensity were determined. The mechanism which describes the effect of the surface on the photoluminescence of quantum wells is governed by the quantum-size Stark effect associated with the surface band bending. The quenching is attributed to an induced electric field, to tunneling of carriers out of a well, and to drift carriers and their nonradiative recombination on the surface. A new high-resolution ( approximately 10 AA) method for determination of the field was developed. In this method a quantum well (located at different distances from the surface) was used as an optical detector of the field intensity. The mainparameters of a depletion layer in the barrier under conditions of strong illumination were determined: The barrier thickness is approximately 500 AA, the charge density is approximately 10/sup 17/ cm/sup -3/, and the band bending is approximately 0.35 eV. The results obtained were important for the understanding of the electron processes that occur in quantum wires and dots formed by etching of planar structures. In particular, the results can be used to account for the photoluminescence quenching observed as a resultof reduction in the dimensions of such nanostructures under the influence of surface electric fields. (21 References)