Optoelectronics, Instrumentation and Data Processing (v.52, #5)

The possibility of improving the performance of semiconductor integrated circuits by replacing the silicon layer in metal–insulator–semiconductor (MIS) transistors by a material with higher charge-carrier mobility. It is shown that germanium is best suited for this purpose based on its properties. Developments made in this area in different laboratories both in Russia and abroad are discussed.
Keywords: field-effect transistor; performance; germanium

A new fabrication route for Ge based metal-insulator-semiconductor (MIS) transistors has been developed based on materials research of dielectric layer compositions. Unwanted impurities were encapsulated in the Ge substrate by using the gate-first process and a modified thermal GeO2 layer with increased viscosity at the interface with the Ge substrate. Increasing the density of the oxide layer near germanium interaction with the deposited Si3N4 film hindered diffusion of the impurities adsorbed by the substrate surface into the transistor channel. This increased the electron mobility in the MIS transistor and prevented its decrease at cryogenic temperatures.
Keywords: Ge planar technology; MIS transistor; gate insulator; germanium oxide modification; silicon dioxide; silicon nitride; germanium nitride

Optimization of the response of nanowire biosensors by O. V. Naumova; B. I. Fomin (434-437).
Nanowire field-effect transistors are highly sensitive sensor elements used for qualitative and quantitative analyses of biological and chemical substances. Optimization of the operation of the sensor is one of the key ways of increasing their sensitivity. An algorithm for choosing the operation mode of sensors based on silicon-on-insulator transistors is proposed which provides their maximum response during conductivity monitoring in the detection of target particles.
Keywords: biosensor; response; field-effect transistor

The current-voltage characteristics (CVC) of PbSnTe:In films with a tin content of x ≈ 0.29 at helium temperatures with unipolar injection from the contacts and limitation by the space charge in a magnetic field of up to 4 T have been studied. Analysis of the CVC has shown that increasing the magnetic field from 0 to 4 T leads to changes in the CVC pattern. A relationship between these changes and the presence of a multilevel system of traps located in the band-gap zone has been suggested..
Keywords: PbSnTe:In solid solution; magnetic field; injection from contacts; epitaxial films

Negative differential resistance in high-power InGaN/GaN laser diode by V. T. Shamirzaev; V. A. Gaisler; T. S. Shamirzaev (442-446).
Negative differential resistance in InGaN/GaN ultraviolet laser diodes is demonstrated. Switching between the lower and upper branches of the S-shaped current-voltage characteristic leads to a change in the optical emission power by six orders of magnitude as the current increases from 3 to 15 mA. The occurrence of a negative differential resistance is explained by superlinear injection of charge carriers of the same sign into the high-resistance InGaN quantum well.
Keywords: laser diode; negative differential resistance

Three-spectrum multielement photodetector device by I. G. Neizvestny; V. N. Shumsky (447-452).
The design and characteristics of a three-spectrum multielement photodetector device with a sensitivity range from 0.6 to 12.0 μm, which consists of three arrays of photodetectors having sensitivity ranges 0.6–0.9, 3–5, and 8–12 μm, are described. Methods of fabrication of photodetector arrays, the photodetector device as a whole, and its photoelectric characteristics are presented.
Keywords: molecular beam epitaxy; heterojunction; p–n junction; sensor; photodetector array; multielement photodetector device

Quantum key distribution in single-photon communication system by D. B. Tretyakov; A. V. Kolyako; A. S. Pleshkov; V. M. Entin; I. I. Ryabtsev; I. G. Neizvestny (453-461).
This paper presents a brief review of experimental studies in quantum cryptography and quantum key distribution by single photons in atmospheric and fiber-optic quantum communication channels. Two experimental setups for quantum key distribution developed at the Rzhanov Institute of Semiconductor Physics SB RAS are described. The dependence of the quantum key distribution rate on the average number of photons μ in the laser pulse was studied. For μ > 0.3, there is a discrepancy between theory and experiment. The reasons for this are, first, the nonzero probability of multiphoton pulses occurring in quantum transmission and counted as single photons by single-photon detectors and, second, the rejection of the cases where several single-photon detectors click simultaneously in quantum key sifting because the measurement result is not determined in these cases.
Keywords: quantum cryptography; quantum key distribution; single photons

Radiation detectors based on PbSnTe:In films, sensitive in the terahertz range of the spectrum by I. G. Neizvestnyi; A. E. Klimov; V. V. Kubarev; V. N. Shumskii (462-474).
This paper presents a review of studies of the photoelectric properties of PbSnTe:In films obtained by molecular beam epitaxy and photosensitive structures in the far infrared and submillimeter ranges based on these films. The parameters of photodetector arrays of this type and detectors based on doped semiconductors and superconductors are compared. One-dimensional (2×128 elements) and two-dimensional (128 × 128 elements) PbSnTe:In based arrays with a sensitivity threshold of ~22 μm and an operating temperature of T ≤ 16 K are implemented. Under background-free conditions, the noise equivalent power (NEP) was NEP ≤ 10−18 W/Hz0.5 at T = 7 K for a black body radiation source at TBB = 77 K. In the submillimeter range of the spectrum, sensitivity to laser radiation with a wavelength λ ≤ 205 μm and a value NEP ≤ 10−12 W/Hz0.5 was observed without optimization of the design of the photosensitive element and minimization of the measurement circuit noise. The directions of the development of PbSnTe:In based radiation detectors are considered..
Keywords: photodetectors; photosensitive devices; infrared range; submillimeter range; PbSnTe:In

Study of photon statistics using a compound Poisson distribution and quadrature measurements by Yu. I. Bogdanov; N. A. Bogdanova; K. G. Katamadze; G. V. Avosopyants; V. F. Lukichev (475-485).
This paper describes the model of a compound Poisson distribution for photon statistics with regard to their bunching in Fock states, thermal states, and others. The method of generating functions is used to calculate the probability distributions, moments, and correlation functions. The parameters of conditional states arising from the subtraction of photons by splitting the beam are determined. The problem of state reconstruction with regard to quadrature quantum measurements is considered. The study is aimed at developing high-precision methods for generating and controlling optical quantum states.
Keywords: quadrature quantum measurements; homodyne detection; compound Poisson distribution; generating functions; photon statistics; thermal states; conditional distributions corresponding to photon subtraction

Formation of silicon nanocrystals in Si—SiO2α-Si—SiO2 heterostructures during high-temperature annealing: Experiment and simulation by I. G. Neizvestny; V. A. Volodin; G. N. Kamaev; S. G. Cherkova; S. V. Usenkov; N. L. Shwartz (486-495).
Experiments and simulations are performed to study the formation of silicon nanocrystals (Si-NCs) in multilayer structures with alternating ultrathin layers of SiO2 and amorphous hydrogenized silicon (α-Si:H) during high-temperature annealing. The effect of annealing on the transformation of the structure of the α-Si:H layers is studied by methods of high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. The conditions and kinetics of Si-NC formation are analyzed by the Monte Carlo technique. The type of the resultant crystalline silicon clusters is found to depend on the thickness and porosity of the original amorphous silicon layer located between SiO2 layers. It is shown that an increase in the thickness of the α-Si layer in the case of low porosity leads to the formation of a percolation silicon cluster instead of individual Si nanocrystals.
Keywords: multilayer structures; nanocrystals; silicon; SiO2 thin films; plasmochemical deposition; Monte Carlo simulation

Raman studies of phase and atomic compositions of GeSi nanosystems after pulsed annealing by A. V. Dvurechenskii; V. A. Volodin; G. K. Krivyakin; A. A. Shklyaev; S. A. Kochubei; I. G. Neizvestny; J. Stuchlik (496-500).
The phase and elemental compositions of GeSi heterostructures deposited on non-refractory substrates are analyzed by using a non-destructive express technique, i.e., the Raman spectroscopy. It is shown that application of pulsed laser annealing allows one to vary the elemental composition and size of nanocrystals formed from solid alloys of germanium and silicon.
Keywords: Raman scattering; phonons; silicon; germanium

Adatom concentration distribution on an extrawide Si(111) terrace during sublimation by D. I. Rogilo; N. E. Rybin; L. I. Fedina; A. V. Latyshev (501-507).
The formation of an adsorption layer on the Si(111) surface during sublimation at temperatures of 1000–1100 °C and subsequent quenching at T = 750 °C is studied by methods of in situ ultrahigh-vacuum reflection electron microscopy and ex situ atomic force microscopy. The adatom concentration distribution on an extrawide (~60 μm) atomically flat terrace is determined for the first time, and the diffusion length xs = 31±2 μm at T = 1000 °C is obtained. The analysis of the temperature dependence of the equilibrium concentration of adatoms near a monatomic step allows pioneering measurements of the energy necessary for adatom detachment from the step and attachment to the terrace E ad ≈ 0.68 eV. Based on these results, the energy parameters for some atomic processes on the Si(111) surface are estimated.
Keywords: silicon; surface diffusion; superstructure; atomic steps; reflection electron microscopy; atomic force microscopy

Monte Carlo simulation of the formation of AIIIBV nanostructures with the use of droplet epitaxy by M. A. Vasilenko; A. G. Nastovjak; I. G. Neizvestny; N. L. Shwartz (508-517).
A Monte Carlo lattice model is proposed to describe the formation of semiconductor nanostructures by the vapor–liquid–solid growth mechanism. This model is used to simulate the growth of GaAs nanostructures by the droplet epitaxy technique in the temperature range from 500 to 600 K in As2 fluxes with intensity of 0.005–0.04 ML/s. The morphology of the formed structures is demonstrated to depend on the growth parameters. Etching of the GaAs substrate by a gallium droplet is studied. The ranges of temperature and As flux rates necessary for the formation of GaAs nanorings are determined. The conditions of the formation of single and double concentric rings are analyzed.
Keywords: droplet epitaxy; nanorings; GaAs; Monte Carlo simulation

Introscopy in nano- and mesoscopic physics: Single electronics and quantum ballistics by V. A. Tkachenko; O. A. Tkachenko; Z. D. Kvon; A. V. Latyshev; A. L. Aseev (518-528).
A method is presented to be used in a computational experiment aimed at studying the internal structure of nano- and mesoscopic objects, i.e., conducting subsystems and quantum phenomena in solid submicron objects, which demonstrate an individual behavior of low-temperature resistance.
Keywords: nanostructures; single electronics; quantum transport; mesoscopics; simulation