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

GaNAs/GaInAs short-period superlattice quantum well structures grown by MOCVD using TBAs and DMHy

We have demonstrated an oxide confinement vertical-cavity surface-emitting laser grown on a GaAs (311)B substrate, and achieved single-transverse mode and single-polarization operation in the entire tested current range. The threshold was 0.6 mA for a 2.7 /spl mu/m/spl times/2.9 /spl mu/m oxide aperture. Even under high-speed modulation up to 5 GHz, the device showed stable single-transverse mode and polarization. Sidemode suppression ratio and orthogonal polarization suppression ratio were over 30 and 10 dB, respectively.

Single-transverse mode and stable-polarization operation under high-speed modulation of InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs (311) B substrate

We have achieved room-temperature pulsed operation of 1.4-µm-wavelength GaInNAs/GaAs double quantum well (DQW) lasers with increased nitrogen composition up to 1.7% grown by chemical beam epitaxy (CBE). A threshold current density of 8.9 kA/cm2 was obtained, and the characteristic temperature (T0) from 10 to 40°C was 94 K.

1.4 µm GaInNAs/GaAs Quantum Well Laser Grown by Chemical Beam Epitaxy

A planar microlens with N.A. = 0.54 has been obtained (Δn = 0.27) by stacking two lenses. The maximally obtainable N.A. is then expected to be ~0.7 but it is limited by aberration, which is discussed theoretically using a Luneburg lens model.

Maximum and effective numerical apertures of a planar microlens.

For the purpose of experimentally and quantitatively demonstrating the enhancement of electron wave reflection by a multiquantum barrier (MQB) consisting of multiple combinations of quarter-de Broglie-wavelength heterostacks, we have fabricated two types of n-GaAs/i-barrier/n-GaAs tunneling diodes with a bulk AlxGa1-xAs barrier and an AlxGa1-xAs/GaAs MQB. From the current-voltage characteristic at 77 K it has been clarified that electrons are well reflected by the MQB. The potential barrier height was virtually increased by the MQB, and is estimated to be about 80 meV, which is in good agreement with theoretical expectation.

Kenichi Iga

Papers

GaNAs/GaInAs short-period superlattice quantum well structures grown by MOCVD using TBAs and DMHy

Single-transverse mode and stable-polarization operation under high-speed modulation of InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs (311) B substrate

1.4 µm GaInNAs/GaAs Quantum Well Laser Grown by Chemical Beam Epitaxy

Maximum and effective numerical apertures of a planar microlens.

Electron Wave Reflection by Multiquantum Barrier