Tailoring of optical phonon modes in nanoscale semiconductor structures: role of interface-optical phonons in quantum-well lasers

This paper discusses the concept of enhancing semiconductor laser performan ce through tailoring of scattering rates of confined polar-optical phonons. Studies of optically pumped intersubband scattering in coupled quantum-wel l lasers have demonstrated that interface-phonon-assisted transitions are i mportant in such structures; furthermore, simple analytical expressions hav e been derived that indicate the importance of interface-phonon scattering in quantum-well lasers. These calculations reveal that the interface-phonon -assisted transitions are dominant for small quantum well dimensions of app roximately 40 Angstrom such dimensions are typical of novel lasers includin g both the unipolar quantum cascade laser and the tunneling injection laser . Recent numerical calculations have confirmed these effects and have exten ded them to indicate how confined and interface phonons also affect critica l laser properties such as optical gain. The application of confined phonon effects to intersubband lasers is one of the most important applications o f confined-phonon physics to the present time. (C) 1999 Elsevier Science B. V. All rights reserved.