MODULATION OF QUANTIZED LEVELS OF GAAS/ALGAAS QUANTUM-WELLS BY INAS MONOMOLECULAR PLANE INSERTION

GaAs/AlGaAs quantum well structures with InAs monomolecular planes are fabricated by flow-rate modulation epitaxy. Photocurrent spectra of these structures are measured to investigate the effect of the InAs planes on the quantized levels. The InAs monomolecular plane inserted at the center of the well shifts the transition peak between the lowest levels (n=1 heavy hole and electron), but does not shift the transition peak between n=2 levels. The amplitude of the wave function for the electrons and holes on the n=2 levels is zero at the center of the well. Therefore, an InAs plane at the center does not modify the distribution of the n=2 carriers. When two InAs planes are inserted in a well and the distance between the two planes is varied, both n=1 and n=2 transition peaks are shifted. Measured spectra are well explained by a finite square well model calculation using the band parameters of GaAs and strained InAs.