320 × 240 CMOS array for the spectral range of 3–5 μm based on PtSi photodiodes

The results of research and development of a 320 × 240 platinum silicide focal plane array (FPA) for the spectral range of 3–5 μm are presented. The development is based entirely on CMOS technology. It is shown that the FPA makes it possible to adjust the photosignal accumulation time at a fixed frame rate and subtract the background constant component in the output device.     

MBE growth and characterization of 5-μm quantum-cascade lasers

Quantum-cascade lasers, which are obtained by molecular-beam epitaxy, emit at wavelengths of 5.0 μm at 77 K and 5.2 μm at 300 K and are based on a design with four quantum wells in the active region with vertical transitions and strain-compensated superlattices with high-efficiency injection and a short lifetime of the ground state are fabricated. The typical thresholds for lasing at 300 K were in the range 4–10 kA/cm². The maximum emission power was as high as ∼1 W, the maximum lasing temperature was ∼450 K, and the maximum characteristic temperature T ₀ ≈ 200 K. The use of a modified process of postgrowth treatment made it possible to reproducibly obtain high-quality devices.     

High-speed photodiodes for the mid-infrared spectral region 1.2–2.4 μm based on GaSb/GaInAsSb/GaAlAsSb heterostructures with a transmission band of 2–5 GHz

High-speed p-i-n photodiodes for the spectral range of 1.2–2.4 μm are fabricated for the first time based on a GaAs/GaInAsSb/GaAlAsSb heterostructure with separated sensitive-(50 μm in diameter) and contact mesas, which are connected by a bridge front contact. The use of an unconventional design for the contact mesa with a Si₃N₄ insulating sublayer 0.3 μm thick under the metal contact made it possible to lower both the intrinsic photodiode capacitance and the reverse dark currents. The photodiodes have a low intrinsic capacitance of 3–5 pF at zero bias and 0.8–1.5 pF at a reverse bias of 3.0 V. The photodiode operating speed, which is determined by the time of increasing the photoresponse pulse to a level of 0.1–0.9, is 50–100 ps. The transmission band of the photodiodes reaches 2–5 GHz. The photodiodes are characterized by low reverse dark currents I _d = 200–1500 nA with a reverse bias of U = ?(0.5–3.0) V, a high current monochromatic sensitivity of R _i = 1.10–1.15 A/W, and a detectability of D*(λ_max, 1000, 1) = 0.9 × 10¹¹ W^?1 cm Hz^1/2 at wavelengths of 2.0–2.2 μm.     

Fabrication of 0.5-μm structures by dry electron lithography and anisotropic plasma etching

A method for the fabrication of submicron (~0.5 μm) structures is presented. It includes the plasma formation of a three-layer mask, electron-beam exposure, plasma development, and anisotropic plasma etching of a resist and silicon oxide. The development in a fluorine-containing plasma forms the negative image of the exposed pattern (a set of parallel strips). The minimum resolution was 0.5 μm at the exposure dose 8 x l0^-4C/cm². The minimum exposure dose at which separate lines are developed was equal to 1 x 10^-4 C/cm²     

IR photodetectors in the range of λ = 1.5–8 μm, based on silicon with multicharged nanoclusters of manganese atoms

It is demonstrated that infrared photodetectors based on silicon with multicharged nanoclusters of manganese atoms can be designed that operate in the wavelength range of ?? = 1.55?C8 ??m. Photodetectors fabricated on such materials have the following parameters: a spectral sensitivity range of ?? = 1.55?C8 ??m, an operating temperature range of T = 77?C250 K, an optimal electric field of E = 5 V/cm, an optimal size of V = 3 × 2 × 1 mm³, a sensitivity threshold of S = 10^?9 W/cm², and a response time of ?? < 10^?6 s.     

On the fractal nature of light-emitting structures based on III–N nanomaterials and related phenomena

It is shown that a three-dimensional fractal–percolation system is formed in nanomaterials of light-emitting InGaN/GaN and AlGaN/GaN structures in the presence of conducting extended defects and local inhomogeneities of the composition of the solid solutions; this system determines the electrophysical properties of light-emitting diodes fabricated on the basis of these structures. The geometry and properties of this system depend nonlinearly on the degree of disorder in the nanomaterial of the structures, on the value of the injection current, and on the rate of alloy growth.     

Influence of thermal annealing on the intensity of the 1.54-µm photoluminescence band in erbium-doped amorphous hydrogenated silicon

Erbium-doped a-Si:H films are prepared by magnetron sputtering of a Si-Er target at a deposition temperature of 200 °C. The films are then subjected to cumulative thermal annealing. A sharp increase (∼50-fold) in the photoluminescence intensity at a wavelength of 1.54 μm is observed after a 15-min anneal at 300 °C in a nitrogen atmosphere. At an anneal temperature ⩾500 °C the photoluminescence signal decreases essentially to zero. The influence of thermal annealing processes is discussed in the context of the model of partial transformation of the structural network of amorphous a-Si(Er):H films. Fiz. Tekh. Poluprovodn. 33, 106–109 (January 1999)     

High-temperature(T = 80℃) operation of a 2μm InGaSb-AlGaAsSb quantum well laser

正An InGaSb/AIGaAsSb compressively strained quantum well laser emitting at 2μm has been fabricated. An output power of 82.2 mW was obtained in continuous wave(CW) mode at room temperature.The laser can operate at high temperature(T = 80℃),with a maximum output power of 63.7 mW in CW mode.     

Design of airport wake vortex monitoring system based on 1.5-μm pulsed coherent Doppler lidar

To shun the vortex hazard,the airport wake vortex monitoring system based on 1.5-mm pulsed coherent Doppler lidar is designed successfully in this paper.Based on the realistic analytical model,the wake vortex generated by airbus A340 under typical flight condition is simulated.Then the principle of airport wake vortex monitoring is introduced,and the work flow of the monitoring system is also presented.Moreover,based on the mechanism of vortex coherent detection and typical system parameters,both detection SNR and detection precision are obtained through numerical simulations.When the system outputs 2 J energy,the coherent detection SNR at 10 km distance is up to 23.452,and detection precision can reach 0.328 m/s.With the wake vortex monitoring experiment of A340,some vortex parameters are estimated.Due to these results comparatively coinciding with the previous simulation conclusions,the ability of Doppler lidar for full-scale wake vortex characterization and real time measurement is demonstrated.The study shows that the wake vortex detection based on 1.5-mm pulsed coherent Doppler lidar has the advantages of high accuracy and far distance,and the designed airport wake vortex monitoring system has proved to be effective and feasible,which has significant development and application prospect in the aspect of assuring flight security and increasing airport capacity.     

Direct calculations on the band offsets of large-lattice-mismatched and heterovalent Si and Ⅲ-Ⅴ semiconductors

Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectron-ic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent ef-fects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as trans-itions,respectively.Taking the Si and Ⅲ-Ⅴ systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mis-matched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and Ⅲ-Ⅴ semiconduct-ors along different directions,it is found that the band offsets of Si/lnAs and Si/lnSb systems in[100],[110]and[111]direc-tions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reli-able and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.     

Investigation of Stimulated Emission from HgTe/CdHgTe Quantum-Well Heterostructures in the 3–5 μm Atmospheric Transparency Window

Semiconductors - Stimulated emission based on interband transitions depending on the pumping wavelength is studied for heterostructures with Hg(Cd)Te/CdHgTe quantum wells in the wavelength region...     

Calculation of the Schottky barrier and current–voltage characteristics of metal–alloy structures based on silicon carbide

A simple but nonlinear model of the defect density at a metal–semiconductor interface, when a Schottky barrier is formed by surface defects states localized at the interface, is developed. It is shown that taking the nonlinear dependence of the Fermi level on the defect density into account leads to a Schottky barrier increase by 15–25%. The calculated barrier heights are used to analyze the current–voltage characteristics of n-M/p-(SiC)_1–x(AlN)_x structures. The results of calculations are compared to experimental data.     

Switching of the photonic band gap in three-dimensional film photonic crystals based on opal-VO<Subscript>2</Subscript> composites in the 1.3–1.6 μm spectral range

The parameters of three-dimensional photonic crystals based on opal-VO₂ composite films in the 1.3–1.6 μm spectral range important for practical applications (Telecom standard) are numerically calculated. For opal pores, the range of filling factors is established (0.25–0.6) wherein the composite exhibits the properties of a three-dimensional insulator photonic crystal. On the basis of the opal-VO₂ composites, three-dimensional photonic film crystals are synthesized with specified parameters that provide a maximum shift of the photonic band gap in the vicinity of the wavelength ∼1.5 μm (∼170 meV) at the semiconductor-metal transition in VO₂.     

Mechanisms of homo- and heteroepitaxial growth of SiC on α-SiC(0001) by solid-source molecular beam epitaxy

Epitaxial growth of SiC on hexagonal (or α)-SiC(0001) has been performed by means of solid-source molecular beam epitaxy (MBE). The solid-source MBE growth conditions have been analyzed concerning the supersaturation and the excess phase formation of silicon and carbon. In general, our results demonstrate that control of the Si/C ratio and the supersaturation (S) is essential for the growth mode and the kind of polytype grown. Low temperature (T<1450K) deposition on on-axis SiC substrates always results in the growth of 3C-SiC, which is significantly improved by an alternating supply of Si and C. On vicinal substrates, a step flow growth mode has been realized at T down to 1300K. In experiments performed at T>1450K under near surface equilibrium conditions, different growth modes, and conditions stabilizing the growth of certain polytypes have been found. With a step decrease of S, a step-flow growth mode of both 4H-and 6H-SiC was obtained and, for the first time in case of epitaxial SiC growth, a homogeneous nucleation of α-SiC at more C-rich conditions has been realized. Conditions stabilizing the growth of certain polytypes have been estimated by thermodynamic calculations considering the influence of polytype structure on the supersaturation and the surface energy. Based on these results, we have demonstrated the growth of a double-heterostructure by firstly growing a 3C-SiC layer on 4H-SiC(0001) at low temperature and a subsequent growth of 4H-SiC under near surface equilibrium conditions on a C-stabilized surface on top of this layer.     

Integration of heterospectral infrared images in the 3–5 and 8–14 μm bands in passive optoelectronic systems with matrix photodetectors

Basic results of the experimental investigation of the correlation between two-dimensional intensity distributions (in two different spectral bands: 3–5 and 8–14 μm) of aerial target and the background on heterospectral infrared (IR) images have been presented. The above images were obtained in the process of comparison tests of trial models of passive optoelectronic systems (OES) with matrix photodetectors (PD) mounted on the antenna of target-tracking radar station (TTRS). A technique for improving the quality of these images was also described. The specified technique was aimed at enhancing the ranges of target detection and recognition under condition of the integration of above images on the basis of the correlation revealed.     

Photosensitivity of thin-film structures based on (CuInSe2)x(2ZnSe)1−x solid solutions

Polycrystalline (CuInSe₂)_x(2ZnSe)_1−x films (x=0.6–1.0) with p-type conductivity and a thickness of 0.5–0.9 μm were obtained by pulsed laser evaporation. It is shown that a chalcopyrite-sphalerite transition occurs in the above system for x=0.7. The obtained films were used to fabricate the photosensitive structure of the In/p-(CuInSe₂)_x(2ZnSe)_1−x and InSe(GaSe)/(CuInSe₂)_x(2ZnSe)_1−x types. Spectral dependences of photovoltaic-conversion quantum efficiency were studied, and the photosensitivity of the structures in relation to the type of energy barrier and the composition was analyzed. It is concluded that the structures under consideration can be used as broadband photovoltaic converters. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 5, 2000, pp. 576–581. Original Russian Text Copyright ? 2000 by V. Rud’, Yu. Rud’, Bekimbetov, Gremenok, Bodnar’, Rusak.     

Influence of Output Optical Losses on the Dynamic Characteristics of 1.55-μm Wafer-Fused Vertical-Cavity Surface-Emitting Lasers

Semiconductors - The results of studying the dynamic characteristics of 1.55-μm single-mode vertical-cavity surface-emitting lasers (VCSELs) formed by the fusion of wafers of high-quality...     

Design and experimental analysis of fiber grating vibration demodulation system based on the 3 × 3 coupler

A novel fiber grating vibration demodulation system, based on 2×2 and 3×3 couplers, is designed. Based on the phase unwrapping algorithm, the three-way asymmetrical output of the 3×3 coupler and demodulation state characteristics of the system when the vibration signal includes high harmonic waves are analyzed in simulations. The result shows that when the three-way output is asymmetrical, the maximum deviation of demodulation signal is 1.625%, and when the vibration signal includes high harmonic waves, the maximum deviation of demodulation signal is 0.9%. The corresponding experiment is conducted. The experimental result shows that the dynamic resolution of the system is 25.22 nɛ / $ sqrt {Hz} $ sqrt {Hz} when the vibration pitch is 5.5 Hz.     

Maskless selective area growth of InP on Sub-μm V-groove patterned Si(001)

Low pressure metalorganic chemical vapor deposition of InP onexactly oriented Si(OOl) substrates with a periodic V-groove pattern of periodicity ≤1.2 μm using a two temperature growth sequence (400 and 640°C) is reported. Planar InP layers with extremely low defect density of 7 × 10⁴ cm⁻² are obtained. For InP on V-grooves of width g ≤1.0μm, a planar surface is formed after less than 1 μm of growth. Formation or suppression of antiphase domains (APDs) is a function of the widths of the (OOl)-oriented ridges. For s ≤1 μm, epilayers are single domain and the direction is oriented parallel to the grooves. At 400°C, nucleation starts homogeneously on {111}-sidewallsand (001)-facets. While heating up to 640°C, InP migrates into the grooves, depleting almost completely the (001)-facets. During growth of the main layer, first the V-grooves are filled up. Subsequently (001)-ridges are overgrown laterally or voids are formed on top of them. This mechanism is responsible for both planarization and APD-suppression. The surface migration length of InP on Si(001) at 640°C is estimated to be ≈0.5 μm.