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We used near-field magneto-photoluminescence scanning microscopy to study structural and optical properties of quantum-dot-like compositional fluctuations in GaAsN and InGaAsN alloys. We show that these fluctuations manifest themselves by the appearance of narrow emission lines (half width 0.5-2 meV) at temperatures below 70 K. We estimated the size, density, and nitrogen excess of individual compositional fluctuations (clusters), revealing phase-separation effects in the distribution of nitrogen in GaAsN and InGaAsN. We found a dramatic difference in the Zeeman splitting of cluster lines between GaAsN and InGaAsN, indicating a strong effect of In on the exciton g-factor., Pub in: Materials Research Society Symposium Proceedings, Volume 692. This article is from ADA405047 Progress in Semiconductor Materials for Optoelectronic Applications Symposium held in Boston, Massachusetts on November 26-29, 2001.

We present an infrared (IR) reflectivity and Raman study of In(x) Ga(1-x)As(1-y)N(y) (x =0 and ^0.08, y ^0.03) alloys grown by molecular beam epitaxy. We observed: strong diagonal Raman components of GaAs-type phonons indicating a local trigonal distortion of the alloy lattice induced by nitrogen ordering; indium induced splitting of the Ga-N type vibration indicating a formation of different local nitrogen atomic arrangements; a sharp (halfwidth^1 cm(-1)) IR mode at 360 cm(-1), of unknown origin., This article is from ADA408025 Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings

We present low-temperature near-field scanning optical microscopy (NSOM) measurements of self-organized InP quantum dots (QD) embedded in a 3lamba/2 GaInP layer. We observed an anomalously strong increase of the emission energy (^27O meV) of a single QD by changing the tip-to-surface distance over ^100 nm in the near-field region. The effect indicates formation of a near-field microcavity having extremely high photon-exciton mixing., Pres: 8th Int Symp Nanostructures: Physics and Technology, St Petersburg, Russia, 19-23 Jun 2000, p232-235. This article is from ADA407315 Nanostructures: Physics and Technology International Symposium (8th) Held in St. Petersburg, Russia on June 19-23, 2000 Proceedings

We report on MOCVD growth of the (In,Al)As-se1f-organized quantum dots (QD) on (Al,Ga)As. We demonstrate that dense arrays (about 2 x 10exp10/cm2) of small ( about 5 nm) QD are formed during annealing (75O C, 20 min, excess of arsine) of In(0.5)Al(0.5)As deposited at 500 C on a Al(0.6)Ga(0.4)As surface as demonstrated by atomic force and transmission electron microscopies and by photoluminescense. We determined that the opening process continues at room temperature and gives rise to large clusters of submicron size after time of one. In contrast, an identical sample that is not annealed shows low density (2 x 10exp9/cm2) of the QDs. Aging in this case gives results in a gradual smoothing of the morphology., Pres: 7th Int Symp Nanostructures: Physics and Technology, St Petersburg, Russia; 14-18 Jun 1999. p525-528. This article is from ADA407055 Nanostructures: Physics and Technology. 7th International Symposium. St. Petersburg, Russia, June 14-18, 1999 Proceedings

We have observed a strong dependence of the intensity of the ordering-induced phonon bands on thermal treatment (rapid cooling and annealing) in Ranmn spectra (RS) of CuPt(sub-B) ordered Ga(0.5)In(0.5)P alloys. The changes of the Raman intensity occur only in diagonal backscattering configuration: y'\\ 1-BAR,1,0, where the polarization of light is parallel to the mirror planes of the ordered structure. We found that there are at least two different intensity distributions of the optical phonon bands the appearance of which is determined by thermal treatment and the alloy film thickness. The bond polarizability model analysis shows that the observed RS behaviour can be described in terms of the order-disorder martensitic transition on trigonal lattice sites., Pres: 6th Int Symp Nanostructures: Physics and Technology, St Petersburg, Russia. 22 Jun 1998, p444-447. This article is from ADA406591 Nanostructures: Physics and Technology International Symposium (6th) held in St. Petersburg, Russia on June 22-26, 1998 Proceedings

In general, fabrication of ridge waveguide lasers is simpler than that of other structures such as diffusion and buried heterostructure lasers. Either wet etching or dry etching processes are generally used for ridge formation. Since the height of the ridge determines the optical confinement as well as the surface recombination and lateral diffusion of the injected carriers, it is important to control the ridge formation properly to optimize the device performance. Recently, an in situ laser-monitored dry etching technique has been widely used in device processing, and various monitoring techniques have been developed to accomplish precise etching-depth control such as growing a stop-etch layer which makes a clear difference in the monitored signal. With the ability of accurate ridge etching, high performance ridge waveguide lasers are expected. However, the reported ridge lasers did not have the low threshold current predicted theoretically even though very good results were obtained for the material threshold current density and for buried heterostructure lasers. This was particularly true for strained-layer InGaAs/GaAs structures.

Surface-normal optical modulators based on III-V semiconductor quantum wells (QWs) and superlattices (SLs) are important for potential applications such as two-dimensional arrays for optical interconnection and optical processing. Asymmetric Fabry-Perot (ASFP) structures utilizing electroabsorption effects of either QWs or SLs inside the cavities sandwiched by a pair of asymmetric mirrors (with bottom mirror more reflective) have been implemented with high contrast ratios. Depending on the active medium and the ASFP configuration, the ASFP can be either normally-on or normally-off., This article is from 'Advanced Processing and Characterization Technologies. Fabrication and Characterization of Semiconductor Optoelectronic Devices and Integrated Circuits Held in Clearwater, Florida on 8-10 May 1991. American Vacuum Society Series 10,' AD-A254 162, p210-213.

This is the second annual report from a research program aimed at exploring technology for optoelectronic integration. The primary goal is to develop technologies critical to the evolution of optoelectronic integrated circuits. Results from new dry etching techniques such as radical beam ion beam etching and laser activated etching will be reviewed, as well as progress on a UHV processing chamber being constructed for use with our MBE systems. Process development on vertical-cavity surface-emitting lasers and modulators is presented, with emphasis on the periodic-gain nipi pumping laser structure. Current results on surface-emitting lasers are presented, covering vertical high-Q cavity structures with InGaAs strained-layer quantum wells as well as 45 etched facet structures. Finally, recent work on quantum-well absorption-edge modification using impurity-free disordering techniques is reviewed.

Optical absorption and thermoluminescence measurements are used to study the x-ray induced reduction of trivalent rare-earth ions to the divalent state in CaF2. Thermoluminescent glow curves for the thirteen available lanthanide ions are measured between 80 degrees and 450K. These are found to be remarkably similar, with glow peaks occurring at nearly the same temperatures for each of the ions. The activation energies for each of the glow peaks is estimated. High resolution measurements of the spectra of each glow peak show that the emission is identical to the fluorescence of trivalent rare-earth ions, and determine the site symmetry of the emitting ion. The results of these spectral measurements can be interpreted in a consistent manner. All of the glow emission below room temperature originates from trivalent rare-earth ions in cubic sites, while the glow spectra above room temperature indicates tetragonal symmetry. Vibrational side bands are observed for some of the ions. In the model proposed to explain this data irradiation at 77K produces divalent rare-earth ions and hole centers. Heating allows a hole to diffuse to the site of a divalent rare earth. The hole and extra electron recombine, leaving an excited trivalent rare-earth ion. Decay of this ion to its ground state results in the observed thermoluminescence. (Author)