A. M. Nadtochiy

Single-spatial-mode semiconductor VCSELs with a nonplanar upper dielectric DBR

Single-spatial-mode semiconductor vertical-cavity surface-emitting lasers (VCSELs) with a non-planar upper (output) dielectric distributed Bragg reflector (DBR) for the 850 nm spectral region are fabricated. The suggested design provides stable single-mode generation in the entire range of working currents, limited by overheating of the active region. Devices with intracavity contacts and a comparatively large current-aperture diameter (5–6 μm) exhibit single-mode lasing at a wavelength of 840–845 nm in the continuous-wave mode at room temperature with threshold currents of 1.2–1.3 mA, a differential efficiency of 0.5–0.55 mW mA−1, and anoutput power of up to 2 mW.

Decreasing parasitic capacitance in vertical-cavity surface-emitting laser with selectively oxidized aperture

Results of a comparative study of the structural parameters and the static and dynamic characteristics of vertical-cavity surface-emitting lasers (VCSELs) with microresonators based on Al0.15Ga0.85As and Al0.8Ga0.2As are presented. It is established that the vertical oxidation of layers in the Al0.8Ga0.2As microresonator during formation of the current aperture leads to a significant increase in the oxide thickness. This leads to a considerable decrease in parasitic capacitance of the device and a 1.7- to 2-fold growth in the cut-off frequency of a low-frequency filter formed by parasitic elements of the equivalent electric scheme of the device.

Determination of the technological growth parameters in the InAs-GaAs system for the MOCVD synthesis of “Multimodal” InAs QDs

The specific features of growth in the InAs-GaAs system by the metal-organic chemical vapor deposition method are studied. The dependences of the In content of the InxGa1 − xAs solid solution and of the InAs growth rate on the molar flow of In in a wide temperature range (480–700°C) are determined. The growth processes of InAs quantum dots (QDs) on GaAs with different surface misorientations are examined. The conditions are found in which InAs QDs are formed with a small number of defects and at a high density on a GaAs “sublayer” grown at a high rate. An epitaxial technique is developed for the synthesis of InAs QDs with multimodal size distribution and an extended photoluminescence spectrum, which can be effectively used in designing solar cells with QDs in the active region.

Effect of the bimodality of a QD array on the optical properties and threshold characteristics of QD lasers

Heterostructures with InGaAs quantum dots (QDs) are synthesized on vicinal GaAs (001) substrates. The photoluminescence (PL) spectra and threshold characteristics of edge-emitting QD lasers are studied in the temperature range 10-400 K. The structural properties of QDs are examined by transmission electron microscopy. Analysis of the PL spectra demonstrates the bimodality of the QD array, which leads to an unusual temperature behavior of the PL spectra and threshold current density. A model of the population of a bimodal QD array by carriers, describing the observed phenomena, is considered.

Dynamic properties of AlGaAs vertical cavity surface emitting lasers with active region based on submonolayer InAs insertions

It has been shown that the use of submonolayer InAs insertions as an active region of AlGaAs vertical cavity surface emitting lasers make it possible to attain resonant frequencies as high as 17 GHz. In this case, single-mode devices with a smaller diameter of the current aperture make it possible to attain higher frequencies at lower current densities than those of multimode devices with a larger aperture diameter. The maximum error-free data transmission rate in the direct modulation mode in NRZ format is 20 Gb/s and is limited by the parasitic cutoff frequency. The high resonant frequency suggests that further optimization of the device design, directed to decreasing the electrical capacitance and resistances, the data transmission rate in lasers based on submonolayer insertions can be increased to 40 Gb/s.

Optical properties of InGaAs/InGaAlAs quantum wells for the 1520–1580 nm spectral range

The optical properties of elastically strained semiconductor heterostructures with InGaAs/InGaAlAs quantum wells (QWs), intended for use in the formation of the active region of lasers emitting in the spectral range 1520–1580 nm, are studied. Active regions with varied lattice mismatch between the InGaAs QWs and the InP substrate are fabricated by molecular beam epitaxy. The maximum lattice mismatch for the InGaAs QWs is +2%. The optical properties of the elastically strained InGaAlAs/InGaAs/InP heterostructures are studied by the photoluminescence method in the temperature range from 20 to 140°C at various power densities of the excitation laser. Investigation of the optical properties of InGaAlAs/InGaAs/InP experimental samples confirms the feasibility of using the developed elastically strained heterostructures for the fabrication of active regions for laser diodes with high temperature stability.

Optical anisotropy of InAs quantum dots

AbstractThe optical anisotropy of InAs quantum dots (QDs) synthesized in the regime of either continuous or submonolayer deposition on a singular GaAs(100) surface have been studied using polarized photoluminescence measurements. It is established that an isolated array of QDs formed in a continuous deposition regime possesses a weak (<1–2%) optical anisotropy, whereas the vertical matching (coupling) of such QDs via less than 15-nm-thick spacer layers leads to an 8% linear polarization of PL along the [0

Laser generation in microdisc resonators with InAs/GaAs quantum dots transferred on a silicon substrate

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