Cryogenic-pressure response of optical transitions in quantum well and bulk GaAs: A direct comparative study

Cryobaric (11-100 K and 300 K, 0-65 kbar) measurements of photoluminescence in GaAs/Al_xGa_1-xAs multiquantum well structures are described. Results on a narrow-well (38 Å wide) structure exhibiting both quantum well and bulk GaAs emission (from a thick buffer region) allow direct comparison of the two for the first time. We find that transitions between Γ-derived n=1 confined levels have the same pressure coefficient, within ±0.2 meV/kbar, as the bulk E₀ gap, 11.4 meV/kbar. An interaction between n=1 electron states and a state 35-40 meV below the X-conduction minima is observed within the pressure-induced Γ-X crossover region for our narrow-well sample. The proposed origin of the latter state is residual interface impurities.