Valence-band structure and transport properties of two-dimensional holes in p-type GaAs/Al 0.5 Ga 0.5 As asymmetric quantum wells under uniaxial compression have been investigated both theoretically and experimentally. The Luttinger-Kohn Hamiltonian with strain terms was self-consistently solved by using the finitedifference k•p method. The Fermi surface was found to become strongly anisotropic under the application of in-plane uniaxial compression, and the differences between the hole concentrations in the ground-state splitted subband and between the corresponding effective masses to decrease. The electrical resistance becomes strongly anisotropic under applied compression, decreasing in the direction parallel to the compression and increasing in the perpendicular direction. ͓S0163-1829͑99͒00408-7͔

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We have carried out a systematic temperature-dependent study of intersubband absorption in InAs/AlSb quantum wells from 5 to 10 nm well width. The resonance energy redshifts with increasing temperature from 10 to 300 K, and the amount of redshift increases with decreasing well width. We have modeled the transitions using eight-band k⋅p theory combined with semiconductor Bloch equations, including the main many-body effects. Temperature is incorporated via band filling and nonparabolicity, and good agreement with experiment is achieved for the temperature dependence of the resonance.

Numerical calculations and experimental results show that, for the broad range of tensile strained p-Al x Ga 1−x As/GaAs 1−y P y /n-Al x Ga 1−x As heterostructures widely used in commercial laser diodes emitting at 766-808 nm, polarization of emitted light may be extremely sensitive to external uniaxial stress due to the change of wave functions symmetry and possible optical transitions in the quantum well levels system. In some heterostructures with quantum well width of 10 nm and phosphorus content below 0.08, TM/TE polarization mode relation showcases a several times decrease and even dominant polarization mode switching under moderate compression of about 5-6 kbar in [100] and [110] directions.

We have studied intersubband transitions in InAs/AlSb quantum wells experimentally and theoretically. Experimentally, we performed polarization-resolved infrared absorption spectroscopy to measure intersubband absorption peak frequencies and linewidths as functions of temperature (from 4 K to room temperature) and quantum well width (from a few nm to 10 nm). To understand experimental results, we performed a self-consistent 8-band k·p band-structure calculation including spatial charge separation. Based on the calculated band structure, we developed a set of density matrix equations to compute TE and TM optical transitions self-consistently, including both interband and intersubband channels. This density matrix formalism is also ideal for the inclusion of various many-body effects, which are known to be important for intersubband transitions. Detailed comparison between experimental data and theoretical simulations is presented.