I. Sela

Excitonic optical nonlinearity induced by internal field screening in (211) oriented strained‐layer superlattices

The nonlinear optical properties of a new class of strained‐layer superlattices (intrinsic Stark effect superlattices) have been investigated. Specifically, we have compared the nonlinear transmission of Ga1−xInxAs‐GaAs strained‐layer superlattices grown along the (211) axis to identical superlattices grown along the (100) axis, and found that the optical nonlinearity in the (211) sample is about one order of magnitude greater than in the (100) sample. A blue shift of the exciton resonance and an increase in the exciton absorption strength in the (211) sample with increasing light intensity was observed (attributed to screening of the intrinsic Stark effect fields by photogenerated carriers), resulting in the stronger optical nonlinearity. The maximum of the nonlinear absorption index, ‖α2‖, in the (211) sample was 54 cm/W (‖Im χ3‖=0.33 esu) whereas in the (100) sample the maximum of ‖α2‖ was 6.9 cm/W (‖Im χ3‖=0.042 esu). The measured carrier recovery time in both samples was 2 ns.

Far-infrared photoresponse of the InAs/GaInSb superlattice

We describe the growth and characterization of the InAs/GaInSb superlattice on GaSb substrates. We present far‐infrared (λ∼10 μm) photoabsorption and photoconductivity spectra which are in good agreement with theoretical predictions for the photoresponse of this spatially indirect superlattice. We report time‐resolved photoconductivity measurements in which two response times are observed. We interpret the fast, 2 ns decay as resulting from electron‐hole recombination via deep defect levels and the slow, 2 μs decay as resulting from recombination of a small fraction of the photogenerated minority carriers which become trapped at a defect site.

Study of interface composition and quality in AlSb/InAs/AlSb quantum wells by Raman scattering from interface modes

We have studied the interface structure and the quality of molecular‐beam‐epitaxy grown AlSb/InAs/AlSb quantum wells through Raman scattering from interface vibrational modes from single quantum wells. A series of samples was grown by varying the growth temperature and the interface composition (by forcing either a light AlAs or a heavy InSb interface bond configuration at each InAs/AlSb interface). We have observed the InSb modes for all the samples and related the intensity and shape of the interface modes to the structure and quality of the interfaces. This work demonstrates that a single interface heterostructure can be probed by Raman scattering.

Raman scattering study of InAs/GaInSb strained layer superlattices

We present a Raman scattering study of the InAs/GaInSb superlattice. This new superlattice is promising as a long wavelength infrared detector material. The samples were grown by molecular beam epitaxy and their structural parameters were determined by Rutherford backscattering and x‐ray diffraction. Samples were grown on [001] GaAs substrates with GaSb buffers, and directly on [001] GaSb substrates. Cross‐sectional transmission electron micrographs show that for the samples grown on GaAs substrates, a high density of dislocations was generated at the GaAs‐GaSb interface, and many of these dislocations thread through the superlattice. The samples grown directly on GaSb had a much lower dislocation density. The Raman spectra of the InAs/GaInSb superlattice shows a single peak, which is a superposition of scattering from the LO phonons in InAs and in GaInSb. For unstrained InAs and GaInSb, the LO phonon energies are sufficiently separated that they would be well resolved in Raman scattering. However, the st...

Nonlinear optical absorption in intrinsic stark effect superlattices

Abstract We have investigated the nonlinear optical properties of a new class of strained-layer superlattices, the intrinsic Stark effect superlattices (ISES). The superlattices consisted of GaInAs/GaAs grown along the (211) B direction. We observed a shift of the excitonic absorotion to higher energies (blue shift) with increasing intensity of the transmitted beam. The observed optical nonlinearity was about one order of magnitude stronger than the one due to excitonic screening in the (100) oriented reference material. This effect is attributed to the screening of the internal electric fields by photogenerated carriers.