Intersubband transitions in conduction band quantum wells: the role of energy band gaps and band off-sets

A new 14-band k/spl middot/p analysis of optical intersubband transitions in conduction band quantum wells demonstrates the importance of the energy band gap and the band off-sets in determining the strength of such transitions, In particular it is found (1) that a narrow band gap enhances the TE activity, and is therefore desirable, because of the importance of band mixing, and (2) that carrier confinement in both the valence band (Type I quantum well) and the upper conduction band is necessary for strong TE activity. This paper discusses these observations and supports these conclusions with measurements made on Type-II InP/InAlAs quantum wells.