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The article reports that exciton localisation in InGaAsN and GaAsSbN observed by near-field magnetoluminescence and scanning optical microscopy (NSOM). Dilute nitride alloys have recently attracted considerable attention as promising materials for laser diodes in the 1.3-1.5 mm range, as well as for more efficient solar cells. The article focuses on use of low-temperature NMPL, at fields up to 10 T, to study these fluctuations in detail. Researchers also employ near-field scanning optical microscopy (NSOM) to study the lateral distribution of such QD-like compositional fluctuations by imaging their individual sharp emission lines.

We report optical measurements (photoluminescence, Raman scattering, and infrared reflectance) of direct band gap and of optical phonon energies of Be[sub x]Zn[sub 1-x]Se alloys grown by MBE on (001) GaAs substrates for a wide range of Be concentrations. The high band gap of BeSe (5.15 eV) suggests the possibility of using isoternary alloys for ultraviolet optoelectronic applications. Be[sub x]Zn[sub 1-x]Se has the unique advantage that it can be lattice matched to Si at about x= 0.5. We observed a strong linear shift of the Be[sub x]Zn[sub 1-x]Se direct band gap to higher energies with increasing Be content (to 3.63 eV for x = 0.34). Furthermore, optical phonon parameters for the entire range of BeSe content have been obtained. Finally, polarized infrared and Raman spectra revealed local atomic ordering (anti-clustering) effects in the group-II sublattice. [ABSTRACT FROM AUTHOR]

Copper and krypton ions have been implanted into Bridgman-grown CdTe crystals. Radiation from tungsten lamps was used to flash anneal the implant damage. Low-temperature photoluminescence analysis of the annealed samples indicates that the annealing provided almost complete repair of the implant damage. However, Cu implants did not significantly increase the activation of this impurity in the lattice when compared with an unimplanted, annealed standard. A comparison of the luminescence spectral changes following annealing at various temperatures of both implanted and unimplanted samples was made. This comparison indicated that activation of Cd site substitutional impurities in the lattice may be limited by the concentration of Cd vacancies generated by the annealing. [ABSTRACT FROM AUTHOR]

Optical-quality GaAs films were successfully grown by molecular beam epitaxy (MBE) through SiO2 insulator windows on GaAs (100) substrates, thus making this selective-area epitaxy applicable to the fabrication of GaAs optoelectronic integrated circuits. The photoluminescence spectra at 2.2 K consist of several exciton peaks near 820 nm and broader acceptor-related peaks centered at approximately 830 nm. The spectra are comparable to those observed in high quality planar MBE GaAs grown in other laboratories. The luminescence intensity from the epitaxial layer above the windows is shown by cathodoluminescence to be much higher than that from the polycrystalline GaAs deposited on top of SiO2. From transmission electron microscopy and x-ray diffractometry it is found that the GaAs grains on the SiO2 grow with their (111) planes preferentially parallel to the SiO2 surface. [ABSTRACT FROM AUTHOR]

We report experimental verification of the prediction of widely bias-tunable below-gap luminescence, from lattice-matched (p) (Al,In)As/ (n) InP heterojunctions, a system that has been predicted to have staggered lineup. The diodes, grown by molecular beam epitaxy, exhibit strong luminescence at 1.4 K, with a peak energy that shifts from 0.97 to 1.04 eV as the (pulsed) current density is increased from 4.5 to 40 A/cm2. Nonshifting injection luminescence at 1.4 eV, due to hole injection into the n-InP substrate, was also present, but appreciably weaker (<25%) than the interface luminescence. The spectra indicate that the band lineup in the (Al,In)As/InP system is indeed staggered, with a residual gap at the interface close to 0.96 eV. The corresponding conduction and valence-band offsets are 0.52 and 0.40 eV. [ABSTRACT FROM AUTHOR]

A self-electro-optic effect device based on a Fabry–Perot reflection modulator has been demonstrated for the first time. This modulator is a normally-off high-contrast asymmetric Fabry–Perot modulator using Wannier–Stark localization in a superlattice. Optical bistability has been achieved with a record-high on/off ratio of 130:1 at the operating wavelength of 7620 Å. The modulator with an appropriate reverse-bias voltage supply was connected in series to a silicon photodiode which when illuminated with an appropriate light source acted as a current source load for the modulator. [ABSTRACT FROM AUTHOR]

We have implemented a novel dry etching technique that combines chlorine radicals generated in a microwave plasma with an argon ion beam. This uniquely provides separate control of the radical flux and ion flux so that the degree of anisotropy and chemical enhancement can be arbitrarily varied. We demonstrate that this etching technique should be capable of producing smooth structures with low damage for applications in optoelectronics. [ABSTRACT FROM AUTHOR]