The study of the noise characteristics of the 89X nm single-mode polarization-stable VCSELs based on InGaAs quantum wells is presented. When VCSEL emission is in resonance with the Cs D1 line, the relative intensity noise (RIN) is -105 dB/Hz at 1 Hz and -155 dB/Hz at 100 kHz. The polarization-resolved RIN is slightly higher than RIN but exhibits similar frequency behavior. The frequency noise is ~10 13 /f Hz 2 /Hz in the 1 Hz < f < 100 kHz range, which corresponds to the emission linewidth of ~30 MHz.

The influence of technological parameters during the local Zn diffusion from the metalorganic source DEZn in the MOCVD reactor on the surface morphology of the InGaAs and InP layers was investigated. For a long-term process (more than 120 minutes) of local Zn diffusion into InP through the InGaAs surface layer, erosion of InGaAs surface was observed regardless of the material of the dielectric mask (SiO2, SiNx), the method of deposition of the dielectric mask (plasma chemical deposition or chemical vapor deposition) and method of etching of the dielectric mask (plasma chemical etching or liquid chemical etching). The effect of lateral Zn diffusion under the dielectric mask was formed on InGaAs/InP heterostructures has been studied. It was found that the depth of Zn diffusion in lateral direction into InGaAs is several times less than the depth of lateral Zn diffusion into InP layer. At the same time, a decrease in the thickness of the InGaAs surface layer leads to an increase in the depth of lateral diffusion of Zn under the mask due to the mechanism of vertical Zn diffusion from the InP:Zn region into the InGaAs surface layer.

The paper presents a study of effect the mesa structure surface passivation on performance of InAlAs/InGaAs/InP avalanche photodiodes. The mesa passivation was made by using treatment in an aqueous solution of ammonium sulfide and subsequent protection by a layer of polyamide (sulfide-polyamide passivation). As a result, avalanche photodiodes with a photosensitive area of 32 microns reproducibly demonstrate dark current below 10-20 nA at the level of 0.9 of the breakdown voltage. A homogeneous distribution of the breakdown voltage value over the sample area at -85V, as well as long-term stability of avalanche photodiode characteristics were observed.

The zinc diffusion process into InP through a thin InGaAs layer using diethylzinc (DEZn) as a p-dopant source was investigated. The distribution profiles of electrically active dopant in InGaAs/InP heterostructures were obtained by electrochemical capacitance-voltage profiling technique. The influence of temperature and pressure in the reactor, DEZn flow rate and process time on the concentration of holes and the diffusion depth was investigated. The process of zinc diffusion strongly depends on the zinc concentration at the surface, however, the maximum concentration of holes and the depth of zinc diffusion into the InP layer might be chosen independently in a certain range of values.

The design features of 8XX nm-range vertical-cavity surface-emitting lasers for providing single-mode and polarization-stable lasing, narrowing the spectral linewidth of laser emission and achieving high modulation bandwidth are considered The special intra-cavity contacted design and the rhomb-shaped oxide-confined aperture can simultaneously provide single-mode output optical power above 1 mW, fixed polarization direction, emission linewidth below 50 MHz and modulation bandwidth more than 5 GHz.

Subject of study. A method for the sulfide-polyamide surface passivation of mesa structures of InAlAs/InGaAs avalanche photodiodes was considered and the static properties of the fabricated crystals of InAlAs/InGaAs avalanche photodiodes were investigated. Aim of study. The study aimed to investigate the effect of sulfide-polyamide surface passivation of mesa structures on the principal parameters of an avalanche photodiode. Method. Sulfide-polyamide surface passivation of a mesa structure entails processing the surface in an aqueous solution of ammonium sulfide followed by the application of a protective layer of AD-9103-30 polyamide. Main results. Avalanche photodiodes based on InAlAs/InGaAs heterostructures were fabricated and investigated. The surface of the mesa structure of avalanche photodiodes underwent sulfide-polyamide passivation. Crystals of avalanche photodiodes with an active area diameter of 32 mu m reproducibly ensured a dark current of 10-20 nA under an applied voltage of 0.9 of the breakdown voltage, uniform distribution of the breakdown voltage value across the sample area, and the long-term stability of parameters. Spectral sensitivity values of the devices in the 1550 nm region were 0.85-0.88 A/W, and their capacitance values were 0.11-0.12 pF. Ensuring the reproducibility and long-term stability of parameters is crucial to passivation technology. Parameter measurements of the avalanche photodiode crystals with sulfide-polyamide passivation performed with a 6-month interval confirmed the temporal stability of the dark current at the level of 5%. Practical significance. The proposed method for the surface passivation of the mesa structure of InAlAs/InGaAs avalanche photodiodes entailing processing in an aqueous solution of ammonium sulfide followed by the application of a protective layer of AD-9103-30 polyamide can be used to fabricate avalanche photodiodes with a reproducible low level of dark current. (c) 2023 Optica Publishing Group

The influence of the substrate temperature and the flux of In adatoms on the structural and optical characteristics of InAs quantum dots with a low surface density is experimentally studied. An increase in the substrate temperature under conditions of a high flux of In adatoms promotes an increase in their surface migration and a certain decrease in the density of the array of quantum dots (down to ~(1-2) 10^10 cm^-2), however, in this case, a significant short-wave shift of the photoluminescence spectrum is observed, despite side points. A decrease in the incident flux of In adatoms at optimum substrate temperatures makes it possible to reduce the dot density more efficiently (down to ~(1-2) 10^9 cm^-2).

The optical characteristics of vertical cylindrical micropillars with AlGaAs distributed Bragg reflectors and InAs/GaAs quantum dots, which are designed for the fabrication of single-photon sources, have been studied. The effect of parameters such as the inclination angle of sidewalls, partial oxidation of AlGaAs layers, and deviation of quantum dots from the central axis of a micropillar on the Purcell factor and the radiation extraction efficiency has been numerically simulated by the finite-difference time-domain method. The allowable ranges of the listed parameters have been determined for cylindrical vertical 920-nm micropillars. The comparison of the calculations performed with the refined refractive indices of the used materials at cryogenic temperatures with the measured characteristics of the fabricated micropillar structures has confirmed the adequacy of the used models.

Electrically-pumped optical microcavity single photon sources based on single quantum dots are investigated by numerical modelling techniques. Design of electrically driven 1.3 μm-range single photon source with intra-cavity contacts and multiply oxide aperture layers is proposed. About two times improvement in photon coupling efficiency into the single-mode fiber is demonstrated as compared with single photon source based on cylindrical micropillar.

Mushroom mesa structure for InAlAs/InGaAs avalanche photodiodes (APD) was proposed and investigated. APD heterostructrures were grown by molecular-beam epitaxy. Fabricated APDs with sensitive area diameter of about 30 micron were passivated by SiN deposition and demonstrate avalanche breakdown voltage Vbr ~ 70-80 V. At applied bias of 0.9 Vbr the dark current was ~ 75-200 nA. The single-mode coupled APDs demonstrate responsivity at a gain of unity is high than 0.5A/W at 1550 nm.

A combination of advanced light engineering concepts enables a substantial improvement in photon extraction efficiency of micro-cavity-based single-photon sources in the telecom O-band at ∼1.3 µm. We employ a broadband bottom distributed Bragg reflector (DBR) and a top DBR formed in a dielectric micropillar with an additional circular Bragg grating in the lateral plane. This device design includes a doped layer in pin-configuration to allow for electric carrier injection. It provides broadband (∼8-10 nm) emission enhancement with an overall photon-extraction efficiency of ∼83% into the upper hemisphere and photon-extraction efficiency of ∼79% within numerical aperture NA=0.7. The efficiency of photon coupling to a single-mode fiber reaches 11% for SMF28 fiber (with NA=0.12), exceeds 22% for 980HP fiber (with NA=0.2) and reaches ∼40% for HNA fiber (with NA=0.42) as demonstrated by 3D finite-difference time-domain modeling.

The impact of transverse optical confinement on the static and spectral characteristics of 1.55 µm vertical-cavity surface-emitting lasers (WF-VCSEL) with a buried tunnel junction (BTJ) n++-InGaAs/р++-InAs/р++-InAlGaAs, implemented using molecular-beam epitaxy and wafer fusion. For lasers with a tunnel junction (TJ) etching depth of ~ 15 nm, it was found that the single-mode lasing occurs up to 8 μm BTJ mesa size due to a relatively weak lateral optical confinement, while the effect of a saturable absorber (SA) appears when the BTJ mesa size is less than 7 µm. Enhancing lateral optical confinement by increasing the BTJ etching depth up to ~ 20 nm leads to suppression of the SA effect at the BTJ mesa size of 5–6 µm, but at the same time limits the maximum single-mode optical power. According to the results of the analysis, an increase in the spectral mismatch between the maximum of the gain spectrum of the active region and the resonance wavelength of the WF-VCSEL up to ~35-50 nm will make it possible to suppress the undesirable SA effect in a wide range of the BTJ mesa sizes maintaining the single-mode lasing.

The possibility of using vertical-emitting lasers with intracavity contacts (IC-VCSEL) and a rhomboidal oxide current aperture for creating a non-zero magnetic field optically pumped atomic magnetometers (OPM) with a 133Cs vapor cell for magnetoencephalographic (MEG) systems were demonstrated. Relative intensity noise (RIN) and polarization resolved RIN of the IC-VCSEL in the 895 nm range with different mirror losses (linewidth) in the frequency range from 1 Hz to 100 kHz were experimentally investigated. Lasers with low mirror loss (narrow linewidth) have polarization resolved RIN comparable to amplitude noise. For IC-VCSEL with an output optical power of 0.8 mW and a linewidth of 55 MHz, the noise level measured is 148 dB/Hz in 1 Hz bandwidth at 40 kHz frequency. The ultimate sensitivity of OPM based on two-beam MX scheme with studied VCSELs was estimated as ~ 11 fT/√Hz.

Using mathematical simulation methods, various versions of the design of electrically-driven single photon sources based on optical microcavities with single quantum dots are investigated. A version of the design of a source of single photons of the 1.3-μm spectral range with intracavity contacts and several oxide-confined apertures layers is proposed, which provides an almost twofold increase in the efficiency of photon coupling to a standard single-mode optical fiber in comparison with a widely used design based on a circular micropillar cavity.

An investigation has been performed of 1.55-μm vertical-cavity surface-emitting lasers based on heterostructures with a buried tunnel junction (BTJ) with a height difference of 15 nm. The devices are obtained by wafer fusion of heterostructures grown by molecular beam epitaxy and provide single-mode lasing at a BTJ diameter of up to 8 μm. A decrease in the BTJ size leads to a sharp increase in the threshold current, the output optical power, and the resonance frequency at the lasing threshold. Stable single-mode lasing takes place due to the smoothed boundary of the buried surface relief, which induces a gradual change in the profile of the effective refractive index in the lateral direction with the effective current confinement retained. This makes it possible to reduce significantly the transverse optical confinement factor for the higher-order modes even at a large BTJ size. However, at a small BTJ size, it leads to the formation of a saturable absorber in unpumped parts of the active region.

High electron mobility transistors (HEMTs) have been developed based on InAlAs/InGaAs heterostructures on an InP substrate, with a transconductance of about 1000 mS/mm, a reverse breakdown voltage of more than 10 V and a unity-gain cutoff frequency is 140 GHz. In addition, HEMT transistors based on AlGaAs/InGaAs/GaAs heterostructures on a GaAs substrate with double gate recessing technology have been developed. This transistors demonstrate a maximum measured transconductance of the current-voltage characteristic of 520 mS/mm, a maximum drain current of 670 mA/mm, and a gate-drain breakdown voltage of 14 V and a unity-gain cut-off frequency is 120 GHz. Due to the increased breakdown voltage, the developed transistors have been used in monolithic integrated circuits of millimeter-wave power amplifiers with an output power of more than 110 mW.

Разработана базовая технология изготовления полупроводниковых однофотонных генераторов для телекоммуникационных диапазонов. Рассмотрены методы реализации генераторов, интегрирующих лазерный источник накачки и излучающую структуру в исполнении, пригодном для внедрения в реальное производство.

The analysis of internal optical loss and internal quantum efficiency in 1.3 μm-range InAlGaAsP/AlGaAs a composite n++-InGaAs/р++-InGaAs/р++-InAlGaAs tunnel junction obtained in the frame of molecular-beam epitaxy and wafer fusion technology. The level of internal optical losses in the lasers under study was varied by depositing a dielectric layer on the surface of the output mirror. It is shown that it is possible in principle to achieve low internal optical loss of less than 0.08% and 0.14% per one pass (round-trip) at temperatures of 20°С and 90°С, respectively.

The design of the n++-InGaAs/р++-InGaAs/р++-InAlGaAs tunnel junction (TJ) for 1.55 μm range vertical-cavity surface-emitting lasers (VCSELs), developed by wafer fusion technique of InAlGaAsP/InP optical cavity with AlGaAs/GaAs distributed Bragg reflectors is proposed and realized. The presence of oxidation-resistant InGaAs layers allows the use of molecular-beam epitaxy at all stages of the heterostructure fabrication, including for regrowth of the TJ surface relief. In the case of using the n++-InGaAs/р++-InGaAs/р++-InAlGaAs TJ, a noticeable increase in the internal optical losses compared to the n++/р++-InAlGaAs TJ design was not obtained. The increase in internal optical loss in lasers can be avoided due to Burshtein-Moss effect in n++-InGaAs layers and thickness minimization of р++-InGaAs layer. As a result, the characteristics of fabricated lasers are comparable with characteristics of VCSELs with n++/p++-InAlGaAs TJ with a similar level of mirror losses.