Photonic crystals and Bragg gratings for the mid-IR and terahertz spectral ranges

A method for the fabrication of 2D periodic structures by contact optical photolithography with image inversion is reported. The optical properties of photonic crystals and Bragg gratings for mid-IR and terahertz emitters are considered. The possibility of raising the integral emission intensity of light-emitting diodes for the mid-IR spectral range is demonstrated. The requirements to gratings for the output of terahertz emission generated by surface plasmons excited in layers of narrow-gap degenerate semiconductors with an accumulation layer are determined.     

Quantum-Cascade Lasers Generating at the 4.8-μm Wavelength at Room Temperature

We report on room-temperature generation at the 4.8-μm wavelength in a lattice-matched structure of a quantum cascade laser (QCL) grown on indium phosphide (InP) substrate. Laser heterostructures grown by molecular beam epitaxy (MBE) comprised 30 cascades and were designed to generate at the 4.80 μm wavelength corresponding to an atmospheric transparency window. Experiments demonstrated effective lasing at temperatures from 80 to 300 K on a wavelength coinciding with the calculated value, which confirmed the high quality of interfaces, high precision of layer thicknesses, and high accuracy of active region doping.     

Manifestation of the Purcell effect in the conductivity of InAs/AlSb short-period superlattices

Vertical transport in short-period InAs/AlSb superlattices with type-II heterojunctions is studied at room temperature. It is found that negative differential conductivity appears in the miniband-conduction mode upon the overlapping of quantum-confined states in a periodic system of quantum wells. In the nonresonant-tunneling mode, equidistant peaks appear on the current-voltage characteristic of these superlattices. These peaks are attributed to the influence of the optical cavity on optical electron transitions in quantum wells (Purcell effect).     

Spin injection in GaAs/GaSb quantum-well heterostructures

GaAs/GaSb type-II quantum-dot heterostructures were grown by molecular-beam epitaxy. The circularly polarized photoluminescence of these samples in a magnetic field up to 4.7 T in the Faraday configuration was investigated. It was found that the emission from quantum dots in a magnetic field is σ⁻-polarized, which corresponds to the electron-spin component along the magnetic-field vector of +1/2. The degree of polarization increases with increasing excitation intensity. The observed effect is explained in terms of spin injection from the GaSb matrix, where spin orientation appears owing to the Zeeman splitting of the conduction band. An increase in the degree of polarization occurs due to a reduction in the charge-carrier radiative lifetime in type-II quantum dots with increasing excitation level.     

Magnetotransport Spectroscopy of the Interface,Quantum Well,and Hybrid States in Structures with 16-nm-Thick Multiple HgTe Layers

Semiconductors - The longitudinal and Hall components of the resistivity tensor are measured in structures with multiple HgTe layers 16 nm thick in magnetic fields to 12 T at temperatures from 1.5...     

A decrease in ohmic losses and an increase in power in GaSb photovoltaic converters

The transmission-line model with radial and rectangular geometry of contact pads has been used to study the contact systems Cr-Au, Cr-Au-Ag-Au, Ti-Pt-Au, Pt-Ti-Pt-Au, Pt-Au, Ti-Au, Ti-Pt-Ag, Ti-Pt-Ag-Au, and Pt-Ag deposited on the p-GaSb surface by the methods of magnetron sputtering and resistive evaporation. It is established that the contact systems Ti-Pt-Ag-Au and Ti-Pt-Ag exhibit the smallest values of the specific contact resistance (ρ _c ≤ 10⁻⁶ Ω cm²), which makes it possible to use these systems in fabrication of photovoltaic converters generating photocurrents with densities as high as 15 A/cm².     

Optically pumped midinfrared (λ = 3.6 μm) light-emitting diodes based on indium arsenide with photonic crystals

It is established that a periodic relief (photonic crystal) created on the surface of an indium arsenide crystal influences the reflection coefficient and the intensity of mid-IR radiation with λ = 3.3–3.6 μm emitted from the active region of an optically pumped InAs-based light-emitting diode.