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We report the first measurements of optical absorption saturation in GaAs/GaAlAs multiple quantum well (MQW) structures at room temperature near the heavy hole exciton peak. Linear absorption shows distinct exciton peaks at room temperature in the MQW and we deduce this is because the confinement increases exciton binding energy without increasing LO phonon coupling. This room-temperature MQW absorption also saturates more readily than that in a comparable GaAs sample; the measured saturation intensity is 580 W/cm2 with a recombination time of 21 ns in a MQW with 102-Å GaAs layers. From this we predict a nonlinear refraction coefficient n2∼2×10−5 cm2/W. This large nonlinearity should permit room-temperature optical devices compatible with laser diode wavelengths, materials and power levels.

We report the determination of Auger recombination coefficients in bulk and quantum well InGaAs by time-resolved luminescence measurements. In bulk InGaAs the coefficient is C=3.2×10−28 cm6/s and has the temperature dependence of the valence-band Auger effect involving the split-off valence band. In 11 nm quantum well InGaAs we find C=0.9×10−28 cm6/s, independent of temperature. The Auger coefficient decreases slightly with decreasing well width.

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We discuss the use of admittance spectroscopy to measure the band offsets of semiconductor heterojunctions. By using this method to analyze the dynamic response of p-n junctions containing lattice-matched InP/Ga0.47In0.53As superlattices we can independently determine both the conduction- and valence-band offsets for this materials system. We find that the sum of these offsets equals the known band-gap difference between InP and Ga0.47In0.53As and that the ratio of the conduction-band offset to the valence-band offset is 42:58.