TYPE-II-]TYPE-I TRANSITION IN (GAX)(N)/(INX)(N)(001) SUPERLATTICES (X=P, SB) AS A FUNCTION OF PERIOD-N

Coherently strained GaX/InX interfaces (X=P, Sb) lattice matched to a (001)-oriented substrate are predicted to have a type-I band-gap alignment, with both the valence-band maximum and the conduction-band minimum (CBM) located on the In-rich material. At the same time, the CBM wave function of short-period (GaX)(n)/(InX)(n) superlattices is predicted to have larger amplitude on the GaX layers, leading to a type-II alignment. We show that (i) a type-II-->type-I transition occurs around the period n=4; (ii) this transition has a different origin with respect to the well-known case of GaAs/AlAs superlattices; (iii) the band structure of ultrathin superlattices cannot be explained in terms of a simple effective-mass theory; (iv) the wave-function localization in short-period superlattices is determined by the atomic orbital energies.