Abstract

The importance of LO phonon emission for intersubband scattering (ISBS) processes is now well established.¹ In very good agreement with theoretical expectations, such a process gives scattering times of 1 ps or less.² The situation is different in wide quantum wells, when the energy separation ΔE₁₂ between the first two subbands is smaller than hω_LO. It has often been proposed that ISBS should then be mediated mainly by acoustical phonons, and be quite slow.’ Such wells would then be promising for laser applications.⁴ However, the demonstration of such a laser failed to be obtained. An explanation was in fact proposed in 1989 by Goodnick and Lugli⁵ who computed carriercarrier induced intersubband scattering. It is clear from their calculations that such ISBS could be as short as a few ps, 100 times faster than acoustic phonons. A number of results have nevertheless been published since then, with scattering times ranging from 1 ps to 1 ns.

© 1999 Optical Society of America