We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Optical properties of metallic films for vertical-cavity optoelectronic devices.

The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

Gan : processing, defects, and devices

1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

The ability to control the modes oscillating within a laser resonator is of fundamental importance. In general, the presence of competing modes can be detrimental to beam quality and spectral purity, thus leading to spatial as well as temporal fluctuations in the emitted radiation. We show that by harnessing notions from parity-time (PT) symmetry, stable single–longitudinal mode operation can be readily achieved in a system of coupled microring lasers. The selective breaking of PT symmetry can be used to systematically enhance the maximum attainable output power in the desired mode. This versatile concept is inherently self-adapting and facilitates mode selectivity over a broad bandwidth without the need for other additional intricate components. Our experimental findings provide the possibility to develop synthetic optical devices and structures with enhanced functionality.

http://science.sciencemag.org/content/sci/346/6212/975.full.pdf

Parity-time–symmetric microring lasers

In this review article a comprehensive analysis of the developments in ultraviolet (UV) detector technology is described. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further considerations are restricted to modern semiconductor UV detectors, so the basic theory of photoconductive and photovoltaic detectors is presented in a uniform way convenient for various detector materials. Next, the current state of the art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to a new generation of UV detectors fabricated from wide band‐gap semiconductors the most promising ...

Semiconductor ultraviolet detectors

A novel approach of on-wafer wavelength control for vertical cavity surface emitting lasers (VCSELs) is proposed using nonplanar metalorganic chemical vapor deposition. The resonant wavelength of 980nm VCSELs grown on a patterned substrate can be controlled in the wavelength range over 45nm by changing the size of circular patterns. We have fabricated linear and 2D multiwavelength vertical surface emitting laser (VCSEL) arrays fabricated by using this technique. The threshold of multi-wavelength VCSELs formed on the patterned substrate is as low as 3 mA. A possibility of an extremely large wavelength span for multi- wavelength arrays will be discussed. The proposed method will be useful for multi-wavelength VCSEL arrays as well as for the cancellation of wavelength nonuniformity across a wafer.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Low-threshold multiwavelength VCSEL arrays fabricated by nonplanar MOCVD

We investigated the effect of the gas flow sequence of dimethylhydrazine (DMHy) at heterointerfaces on the optical quality of GaInNAs/GaAs grown by metalorganic chemical vapor deposition (MOCVD). We point out that the photoluminescence (PL) degradation of GaInNAs grown by MOCVD can be categorized into two types. One is the formation of a GaNAs layer at the interface which causes both an unexpected wavelength extension and degradation of crystal quality. Another is introduction of non-radiative centers by N incorporation itself. To overcome these degradation mechanisms, the insertion of GaInAs to the GaInNAs/GaAs heterointerface is proposed. A GaInAs intermediate layer (IML) suppresses GaNAs formation and improve the optical quality of GaInNAs QWs.

http://ieeexplore.ieee.org/iel5/7389/20085/00929210.pdf

Photoluminescence dependence on heterointerface for MOCVD grown GaInNAs/GaAs QWs

III-V semiconductor photonic crystals are expected to achieve an ultimate high efficiency in light emitters. However, due to the difficulty of fabrication, only a few groups have succeeded in observing the photonic bandgap (PBG) in small crystals designed for lightwaves. In addition, the most important issues, i.e., modulation of spontaneous emission intensity and lifetime, have never been evaluated. In the study, we fabricated 2-D photonic crystals of fine micro-columns into a GaInAsP/InP MQW wafer and observed the PBG at /spl lambda/<1.6 /spl mu/m. From the measurement of spontaneous emission intensity and lifetime, we found a strong enhancement of extracted spontaneous emission from the photonic crystals.

Strong enhancement of extracted spontaneous emission from GaInAsP 2-D photonic crystals

In this study, we demonstrate 960 nm single-mode VCSEL arrays grown on a GaAs (311)B substrate. All the devices in a 3/spl times/3 array exhibited single-transverse-mode and stable-polarization operation in an entire injection current range. Moreover, we investigated the dynamic characteristics such as time-resolved orthogonal polarization suppression ratio (OPSR) and 2.5 Gbit/s NRZ through a multi-mode fiber data transmission.

Single-transverse mode and stable-polarization operation of GaInAs/GaAs vertical-cavity surface-emitting laser array on GaAs (311)B

A simple index-distribution measurement method using scanning total reflection (STR) is presented On the basis of preliminary experiments, its accuracy confirmed to be 01% with a spatial resolution of 2 µm Further considerations show that the theoretical limits of these values can be better than 001% and 1 µm, respectively The results of rod lenses measured by the STR method and the interference method coincided well, and good measurement reproducibility was confirmed The index profile of a planar microlens was measured and the result was found to coincide with a theoretically predicted result

Kenichi Iga

Papers

Low-threshold multiwavelength VCSEL arrays fabricated by nonplanar MOCVD

Photoluminescence dependence on heterointerface for MOCVD grown GaInNAs/GaAs QWs

Strong enhancement of extracted spontaneous emission from GaInAsP 2-D photonic crystals

Single-transverse mode and stable-polarization operation of GaInAs/GaAs vertical-cavity surface-emitting laser array on GaAs (311)B

A Scanning Total Reflection Method for Refractive-Index Profiling