Volume 91, Issue 11, 01 June 2002
Index of content:
Digitally graded active region for optically pumped intersubband lasers and nonlinear wavelength convertors91(2002); http://dx.doi.org/10.1063/1.1476067View Description Hide Description
A strategy is proposed for the realization of quantum-well structures optimized for devices based on intersubband optical transitions. It relies on the recently established techniques for the design of optimal smooth quantum-well profile by using the inverse spectral theory, followed by the design of an (almost) equivalent digitally graded structure, comprising just two different alloy compositions. Digital grading greatly simplifies the structure growth while essentially fully retaining the properties achieved in smoothly graded optimized structures. Example designs are presented for an optically pumped quantum-well laser and for a quantum well intended for the second-harmonic generation.
91(2002); http://dx.doi.org/10.1063/1.1469688View Description Hide Description
Angular-resolved photoluminescencespectra have been obtained from polymer-made opaline photonic crystals impregnated with Coumarin dye. Spectral changes with optical excitation power and the direction of detection have been analyzed. The anisotropy in the suppression of the spontaneous emission is shown to be in accord with the Bragg stop-band dispersion.
91(2002); http://dx.doi.org/10.1063/1.1477282View Description Hide Description
The relaxation of strain in the ZnS epilayers grown on (100) GaP was investigated with resonant Raman scatteringmeasurement. The single LO phonon resonant Raman shift and the intensity increased but the full width at half maximum decreased with the increasing ZnS epilayer thickness. These were attributed to the relaxation of the biaxial tensile strain with the generating misfit dislocations. Finally, the critical thickness of ZnS/GaP epilayer was found to be around 35 nm.
91(2002); http://dx.doi.org/10.1063/1.1471383View Description Hide Description
Transient photovoltage (PV) measurements have been carried out on free-standing porous silicon of different porosity. For porous silicon of low porosity, fast charge-carrier separation takes place in the surface space-charge region. A retarded component arises in the PV transients due to limitation of the separation of charge carriers by interparticle transport. For nanoporoussilicon, the fast component is absent and the PV transients are retarded strongly in time. The maximum of the retarded PV transients is correlated with the dielectric relaxation time which was obtained by using dc conductivity measurements. This opens opportunities to a contactless electrical characterization of porous semiconductors and its application.