NONPARABOLICITY AND A SUM-RULE ASSOCIATED WITH BOUND-TO-BOUND AND BOUND-TO-CONTINUUM INTERSUBBAND TRANSITIONS IN QUANTUM-WELLS

A sum rule for electronic intersubband transitions has been derived fo llowing Kane's model, beyond the quadratic dispersion relations. The s um rule takes into account the effects of nonparabolicity and the diff erent effective masses in the well and barrier materials; it depends o n the property of the ground state of the system and, as such, on the shape of the potential. The boundaries of the validity of matrix eleme nt computations are also discussed in the case where only the conducti on band is included. Experimental results are presented for bound-to-b ound and bound-to-continuum intersubband transitions in various types of Al0.48In0.52As/Ga0.47In0.53As quantum well systems (single wells, c oupled wells, and quantum wells with Bragg confinement); the agreement with theory is excellent. In the last section of the paper, the effec t of the electric field on the sum rule is investigated.