Patent ID: 8179585

Claim:
A semiconductor coupled quantum structure, comprising: at least a coupled quantum well structure disposed on a substrate, wherein a coupling barrier layer disposed between quantum well layers has a band-offset (ΔE c1 ) that is smaller than band-offsets (ΔE c2 ) of the quantum well layers and outer barrier layers, the smaller band-offset (ΔE c2 ) is smaller than one selected from a plurality of excitation levels (E 4 and E 3 ), and is larger than one ground level selected from a plurality of ground levels (E 2 and B 1 ), wherein the quantum well layers comprise InGaAs; the coupling barrier layer comprises InAlAs or InAlGaAs; the outer barrier layer comprises AlAsSb; and all of the intersubband energy differences in the conduction band of the coupled quantum well structure is 36 meV or more.