Strong emission from As monolayers in AlSb

Strong photoluminescence (PL) bands between 1.41 and 1.62 eV have been observed 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 dependence on the SL period but shifts significantly to higher energy with decreasing AlAs thickness. Optically detected magnetic-resonance (ODMR) experiments at 24 GHz on the 1.45-eV PL from the SL's with similar to 1 ML of AlAs 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 derived 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 sample with 31 ML of AlSb and 0.27 ML of AlAs. The PL and ODMR results can be 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 and the strength of the exchange interaction reflect the degree of wave-function penetration into the adjacent AlSb barriers. The weakly bound excitons are localized at fluctuations along the AlSb/AlAs interfaces. [S0163-1829(99)00303-3].