The effects of the isoelectronic Al-doping of GaN grown by metal organic chemical vapor deposition were investigated for the first time using scanning electron microscopy (SEM), Hall measurements, photoluminescence (PL), and time-resolved PL. When a certain amount of Al was incorporated into the GaN films, the room temperature photoluminescence intensity of the films was approximately two orders larger than that of the undoped GaN. More importantly, the electron mobility significantly increased from 130 for the undoped sample to 500 cm2/Vs for the sample grown at a TMAl flow rate of 10 νmol/min, while the unintentional background concentration only increased slightly relative to the TMAl flow. The incorporation of Al as an isoelectronic dopant into GaN was easy during MOCVD growth and significantly improved the optical and electrical properties of the film. This was believed to result from a reduction in the dislocation-related non-radiative recombination centers or certain other defects due to the isoelectronic Al-doping.

Ensembles of homogeneous self-assembled quantum dots (QDs) and nanoholes are fabricated using molecular beam epitaxy in combination with atomically precise in situ etching. Self-assembled InAs QDs with height fluctuations of ±5% were grown using a very low indium growth rate on GaAs (001) substrate. If these dots are capped with GaAs at low temperature, strong room temperature emission at 1.3 νm with a linewidth of 21 meV from the islands is observed. Subsequently, we fabricate homogeneous arrays of nanoholes by in situ etching the GaAs surface of the capped InAs QDs with AsBr3. The depths of the nanoholes can be tuned over a range of 1-6 nm depending on the nominal etching depth and the initial capping layer thickness. We appoint the formation of nanoholes to a pronounced selectivity of the AsBr3 to local strain fields. The holes can be filled with InAs again such that an atomically flat surface is recovered. QDs in the second layer preferentially form at those sites, where the holes were initially created. Growth conditions for the second InAs layer can be chosen in such a way that lateral QD molecules form on a flat surface.

Dilute nitride GaInNAs alloys grown on GaAs have quickly become an excellent candidate for lower cost 1.3-1.55νm vertical cavity surface emitting lasers (VCSELs) and high power edge emitting lasers in the past few years. Despite the relative immaturity and challenges of this new materials system the results have been very promising. Some of the material challenges include the limited solubility of nitrogen in GaAs, non-radiative defects that may be caused by nitrogen incorporation, and characterization of the unique set of properties nitrogen adds to this metastable alloy. In addition, a new component has been added in order to improve epitaxial growth and optical properties at wavelengths longer than 1.3νm. By adding Sb to the alloy, luminescence has been greatly enhanced between 1.3-1.6νm where normally poor quality material results. This paper describes some of the material challenges and progress in devices based on the GaInNAs and GaInNAsSb system.

We report the role of thin AlN interlayer in the fabrication of AlxGa1-xN/GaN heterostructures with high x from 0.35 to 0.50 on sapphire (0001) by MOVPE. After growing the AlN interlayer of 20 nm thick on GaN/sapphire (0001) epitaxy, the AlxGa1-xN epitaxial layers of 1.0 um thick were grown on it with increasing the flow rate of TMA. The measured Al mole fractions of AlxGa1-xN/GaN heteroepitaxy grown using the thin AlN interlayer from each TCD rocking curve are 0.35, 0.37, 0.45 and 0.50, respectively. As incorporation rate of Al in the AlxGa1-xN increases, the crystallinity is getting well and the RMS values scanned by AFM of their surfaces become lower. And also, the optoelectronic characteristics of those heteroepitaxy evaluated by cathodeluminescence(CL) are improved with the increase of x. To the contrary these trends, it is usually known that crystallinity, surface morphology and optical property of the AlxGa1-xN/GaN heteroepitaxy grown without AlN interlayer between them become worse with the increase of x above 0.2. Meanwhile, electrical resisitivities of Al0.35Ga0.65N, Al0.37Ga0.63N, Al0.45Ga0.55N and Al0.50Ga0.50N epitaxy, which were grown with the thin AlN interlayer, measured by four point probing method are 13.5, 18.1, 31.7 and 36.2 Mohm-cm, respectively. These resisitivities increase by degrees in spite of the advance of characteristics with the raising of x.

We study the influence of optical near-field interactions on the dipole surface plasmon resonance of Au nanoparticles in closely spaced particle arrays using finite-difference timedomain simulations. In particular, the resonance energies of the collective plasmon-polariton modes are determined for longitudinal and transverse polarization for different particle array lengths and inter-particle spacings of 50 nm Au spheres in air. The obtained results are set in context with recent publications suggesting the possibility to use ordered arrays of closely spaced noble metal nanoparticles as plasmon waveguides for electromagnetic energy below the diffraction limit of light.

A channel add-filtering function of a device based on defects in a two dimensional photonic crystal slab is investigated in addition to a channel drop-filtering function reported previously. It is considered that photons irradiated to a point defect from free space are trapped by the point defect, are transferred to a line defect waveguide nearby, and are emitted from the waveguide edge. It is shown that the spectrum of the add-filtering function is almost same as that of the drop-filtering function, which demonstrates that photons can be not only dropped-from but also added-to a line-defect waveguide through the resonant trapping by point defects.