An exact analytical representation has been obtained for electron eigenstat
es in the full isotropic 8-band Kane model and applied to calculate the dep
opulation rate of the lower lasing state in the active region of a type-II
intersubband cascade laser. We show that interband tunneling rate takes its
maximum value when the depopulated states belong to the upper of the coupl
ed electron- and hole-like subbands in the "leaky window" of the broken-gap
InAs/GaSb heterostructure. (C) 2001 Elsevier Science B.V. All rights reser
ved.