Strong photoluminescence (PL) bands between 1.41 and 1.62 eV have been obse
rved from superlattices (SL's) composed of fractional or single monolayers
(ML) of AlAs separated by 22-49 ML of AlSb. The emission exhibits a weak de
pendence on the SL period but shifts significantly to higher energy with de
creasing AlAs thickness. Optically detected magnetic-resonance (ODMR) exper
iments at 24 GHz on the 1.45-eV PL from the SL's with similar to 1 ML of Al
As reveal S = 1/2 electron spin transitions with g(parallel to) = (1.916- 1
.923) +/- 0.002 and g(perpendicular to) = (1.934- 1.944) +/- 0.002 split by
an exchange interaction (Delta) of (3.4-8.0) +/- 0.2 mu eV with holes deri
ved from the J(z)= +/- 3/2 valence band. Exchange-split electron resonances
with g(parallel to) = 1.868+/-0.002 and g(perpendicular to) = 1.882 +/- 0.
002 and Delta = 19.5+/-0.5 mu eV were detected on the 1.62-eV band from a s
ample with 31 ML of AlSb and 0.27 ML of AlAs. The PL and ODMR results can b
e understood using a type-II band lineup with the electron localized at the
AlAs ML and the hole excluded to the AlSb layers. The electron g values an
d the strength of the exchange interaction reflect the degree of wave-funct
ion penetration into the adjacent AlSb barriers. The weakly bound excitons
are localized at fluctuations along the AlSb/AlAs interfaces. [S0163-1829(9
9)00303-3].