320 × 256 avalanche array photodetector on the basis ternary alloys of the A
3
B
5
group with an InGaAs absorbing (in the band of 0.9–1.7 μm) layer and InAlAs barrier layer is studied. The array of ...320 × 256 elements was fabricated in a nBp nanoheterostructure by the mesa technology. The number of imperfect elements, the dependence of the dark current on the bias voltage, and the avalanche gain factor are measured.
Photoelectric properties of different stressed InGaAs/AlGaAs heterostructures with quantum wells grown by the method of molecular beam epitaxy on GaAs substrates for mid-wavelength infrared ...largeformat photodetector arrays operating in the spectral range 3–5 μm have been investigated. It has been shown that the change in the composition of barrier layers leads to a significant shift of the photosensitivity spectra of such heterostructures.
Modern trends in the technology of Cd
x
Hg
1–
x
Te-based photosensitive barrier structures for the middle and far infrared bands, which can operate at near-room temperatures, are analyzed. Main ...approaches to solving the problem of increasing the photodiode-detector operating temperature have been considered and analyzed.
Photoelectric characteristics of a 320 × 256-element focal plane array (FPA) with a pitch of 30 μm, whose photosensitive element is formed in the InSb epitaxial layer deposited on a heavily doped ...substrate, have been investigated. For a relative aperture of 1: 0.94 and an integration time of 1.46 ms, the mean value of the noise-equivalent temperature difference is 10.5 mK, the percentage of defective elements is 0.12%, and the correction time is more than 3 h. The FPA has been compared to similar commercial devices based on bulk InSb.
This paper deals with the second part of the overview on analytical calculations of the characteristics of avalanche photodiodes (APDs) based predominantly on direct gap semiconductors. In the first ...part of the overview (JCTE 2017, vol. 62, no. 9, p. 1027), a general formulation of the problem is carried out and an approach to its solution is reported. The program for calculations of multiplication coefficientins is fulfilled. In the most typical situations, they are represented analytically. It is demonstrated that the obtained analytical results are in good quantitative agreement with previously published numerical calculations and experimental data. In the given part of the overview, the dependences between the interband tunnel current of the heterostructure with a
p
+
–
n
junction in the “wide-gap” (wg) layer and the parameters of used semiconducting materials, layer-doping levels, and their thicknesses corresponding to avalanche breakdown voltages of a heterostructure are analyzed theoretically. It is demonstrated that, as a rule, the tunnel current depends nonmonotonically on the dopant concentration in the “high-resistance” region of a wg layer. There is an optimal concentration of the given dopant at which the tunnel current reaches its absolute minimum. Simple formula for determining the optimal concentration is derived. In addition, an analytical expression for determining the minimum tunnel current is obtained. In real cases, tunnel currents can vary by several orders of magnitude. It is found that, in many cases, an increase in the doping level of a “narrow gap” layer diminishes the tunnel current. It is shown that the tunnel current does not vanish with a decrease in the doping level of the high-resistance layers of a heterostructure but, beginning with a certain concentration, becomes independent of the doping level. An analogous effect is inherent to a homogeneous
p
+
–
n
junction. Physical reasons of such behavior of tunnel currents, which are observed at an avalanche breakdown voltage, are discussed. A technique for the optimizing the parameters of the APD heterostructure with separate absorption and multiplication regions (SAMRs) is developed. As an example, specific calculations are carried out for a widely used InP–In
0.53
Ga
0.47
As–InP heterostructure. The opportunity of description of transient phenomena in
p–i–n
APDs is considered first of all in the case where the initial voltage
V
0
is higher than the avalanche breakdown voltage
V
BD
. This problem is formulated because there is a need to know the explicit conditions whereby the Geiger mode is generated in APD operation. A formula describing the total time of progress in the avalanche Geiger process is derived. An analytical expression for the implementation of the Geiger mode is presented. At the end of the given paper, the advantages of avalanche heterophotodiodes with SAMRs of the low-high-low type over classical samples are demonstrated and discussed on the basis of analytical calculations. The numeration of formulas, figures, and references continues that used in Part I.
The state-of-the-art of the development of photodetectors and photoreceiving devices operating in the range of electromagnetic radiation 0.1–0.38 μm is presented. A review of the world achievements ...and tendencies in the development of this field of photoelectronics based on various semiconducting materials is presented. Main physical and engineering problems of the development of ultraviolet photodetector modules designed on the basis of the А
III
-N compounds are considered.
Topological solitons occur in many nonlinear classical field theories. They are stable, particle-like objects, with finite mass and a smooth structure. Examples are monopoles and Skyrmions, ...Ginzburg-Landau vortices and sigma-model lumps, and Yang-Mills instantons. This book is a comprehensive survey of static topological solitons and their dynamical interactions. Particular emphasis is placed on the solitons which satisfy first-order Bogomolny equations. For these, the soliton dynamics can be investigated by finding the geodesics on the moduli space of static multi-soliton solutions. Remarkable scattering processes can be understood this way. The book starts with an introduction to classical field theory, and a survey of several mathematical techniques useful for understanding many types of topological soliton. Subsequent chapters explore key examples of solitons in one, two, three and four dimensions. The final chapter discusses the unstable sphaleron solutions which exist in several field theories.
Ovaj rad predstavlja rezultate šestogodišnjeg projekta čiji je jedan od ciljeva bio promotriti s kojim konceptualnim razumijevanjem Newtonove mehanike učenici upisuju preddiplomske studije na kojima ...od samog početka studiraju fizikalne kolegije. Kao primjer takvih studijskih programa, istraživanjem je obuhvaćeno 977 studenata prve godine sveučilišnih studija: Farmacija (N = 152); Kemija i kemijska tehnologija (N=563); Prehrambena tehnologija (N=123) i stručnog studija Zaštita i oporaba materijala (N=139). Mjerni instrument korišten za procjenu studentskoga stupnja znanja Newtonove mehanike je Force Concept Inventory (FCI test). Kod svi nastavnih programa promatranih preddiplomskih studija fizikalni kolegiji temeljni su kolegiji i stoga zahtijevaju značajan angažman i studentsko znanje kako bi se uspješno savladali. Rezultati pokazuju da upisani studenti dolaze s izuzetno slabim znanjem Newtonove mehanike na promatrane studije. Kod studenata preddiplomskog studija Faramacija 9,9 % studenata je na razini Newtonovskog razmišljanja; kod preddiplomskog studija Kemija i kemijska tehnologija njih 0,9 %, kod preddiplomskog studija Prehrambena tehnologija 4%, dok kod preddiplomskog stručnog studija Zaštita i oporaba materijala nema upisanih studenata koji su usvojili Newtonovu mehaniku. Ovi rezultati ukazuju na značajne probleme u srednjoškolskoj nastavi fizike kao i probleme u kvalitetnom savladavanju gradiva fizikalnih kolegija na promatranim studijima.
Experimental results of the investigation and analysis of structural properties of cadmium–zinc–tellurium (CZT) substrates intended for the cadmium–mercury–tellurium (MCT) epitaxy by the methods of ...X-ray diffraction, selective etching, and infrared (IR) microscopy are considered. A relation between the shape and the full width at half-maximum (FWHM) of the rocking curve with structural defects, which are present in the material, is demonstrated. Precipitates and inclusions of the second phase, which are present in the substrate material in the amount of 10
2
–10
4
cm
–2
, do not affect values of the FWHM of the rocking curve. Broadening of the rocking curve is caused by either high density of dislocations (>8 × 10
5
) or the cellular property of their distribution. Maps of the FWHM distribution of the rocking curve for determination of structural perfection throughout the entire areas of the samples allowing evaluation of the suitability of wafers for subsequent technological process have been made.
Methods for measuring the current-voltage characteristics (
I–V
curves) of photodiodes in a 6 × 576 mercury-cadmium-tellurium (MCT) multirow photodetector designed for operation in the longwave part ...of the infrared (IR) spectral range are analyzed. The
I–V
curve is plotted using the resultes of measurements of output signals of a large-scale readout integrated circuit (ROIC) hybridized with a row of IR photodiodes. The method of independent current measurement at each point of the
I–V
curve is compared to the method of additive current measurements. A method of determining optimum working points of photodiodes by plotting and analyzing the dependence of the differential resistance of photodiode on the bias voltage is proposed. Distributions of photodiode currents for a sample of a 6 × 576-element focal plane array (FPA) based on MCT photodiodes with a
p
-type conductivity substrate having the cutoff wavelength of λ
0.5
= 10.5 μm are considered.
