TYPE-I AND TYPE-II ALIGNMENT OF THE LIGHT-HOLE BAND IN IN0.15GA0.85ASGAAS AND IN IN0.15GA0.85AS/AL0.15GA0.85AS STRAINED QUANTUM-WELLS/

We present results of photoluminescence and cathddoluminescence measur ements of strained undoped In0.15Ga0.85As/GaAs and In0.15Ga0.85As/Al0. 15Ga0.85As quantum well structures, designed to throw light on the cur rent controversy ever light-hole band alignment at low In content. We compare these data with. theoretical calculations of the confined stat e energies within the eight band effective mass approximation, Our ana lysis shows that for In0.15Ga0.85As/GaAs, the observed two transitions are consistent with either type I or type II alignment of the light h ole band for band offset ratios within the accepted range. In the case of In0.15Ga0.85As/Al0.15Ga0.85As, however, our results clearly indica te type II alignment for the light hole band, We derive the band offse t ratio Q, defined here as Q = Delta E-c/Delta E-g where Delta E-c is the conduction band offset and Delta E-g is the bandgap difference bet ween the quantum well and the barrier in the presence of strain, for t he In0.15Ga0.85As/Al0.15Ga0.85 as system to be Q = 0.83 and discuss it in the context of the common anion rule.