Розглянуто механізми імпульсного лазерного твердофазного легування CdTe індієм при створенні діодних структур для детекторів рентгенівського і гамма-випромінювання. Показано, що масоперенос індію в CdTe при наносекундному лазерному опроміненні структури Іn–CdTе до порога плавлення CdTe відбувається за механізмом бародифузії – внаслідок значного градієнта напружень. Розраховано коефіцієнти масопереносу індію та оцінено середню дрейфову швидкістьпереміщення атомів Іn в CdTe під час опромінення наносекундним імпульсом ексимерного лазера структури Іn–CdTe з товщиною плівки Іn 30 нм при оптимальному для легування значенні густини енергії E = 100 мДж/см2.

Laser photothermoacoustic transformation in sensor semiconductor structures was experimentally and theoretically investigated. An expression for a pressure pulse describing the evolution of an ultrasonic response excited by a nanosecond laser pulse with a Kummer-Gaussian intensity distribution was obtained. The possibility of effective control of photothermoacoustic transformation of laser pulses in semiconductor structures used for creating highly sensitive detectors of ionizing radiation was experimentally demonstrated.

We theoretically and experimentally investigated the process of laser photothermoacoustic transformation in sensor semiconductor structures. We obtained the expression for a pressure pulse describing the evolution of an ultrasonic response excited by a nanosecond laser pulse with a Kummer-Gaussian intensity distribution. The possibility of effective control of the process of photothermoacoustic transformation of laser pulses in semiconductor structures used for creating highly sensitive detectors of ionizing radiation was experimentally demonstrated.

Електричні та люмінесцентні характеристики світлодіодів ультрафіолетового випромінювання 365 нм при Т = 77 К / В.П. Велещук, О.І. Власенко, З.К. Власенко, І.В. Петренко, Є.В Малий, М.П. Киселюк, О.В. Шефер, В.В. Борщ // Збірник тез конференції молодих вчених з фізики напівпровідників «Лашкарьовські читання» з міжнародною участю, Київ, 3-5 квітня 2019. – К. : ІФН НАНУ, 2019. – C. 44.

Electrical and Luminescence Properties of Ultraviolet LEDs 365-400 nm / V.P. Veleschuk, A.I. Vlasenko, Z.K. Vlasenko, V.V. Shynkarenko, Ya.Ya. Kudryk, V.V. Borshch, O.B. Borshch, A.V. Shefer, M.P. Kisselyuk // XVII International Freik Conference Physics and Technology of Thin Films and Nanosystems : abstract book. – Ivano-Frankivsk : Vasyl Stefanyk Precarpatian national University, 2019. – P. 294.

Current-voltage characteristic and electroluminescence of UV LEDs 365 nm at liquid nitrogen temperature / V. Veleschuk, A. Vlasenko, Z. Vlasenko, . Petrenko, Y. Malyi, V.V. Borshch, O.B. Borshch, A.V. Shefer // Optica Applicata. - 2019. - Vol. 49, № 1. - P. 125-133. - URL: http://opticaapplicata.pwr.edu.pl/article.php?id=2019100125

Borshch V.V. Electroluminescence of InGaN/GaN heterostructures at the reverse bias and nitrogen temperature // V.V. Borshch [et al.] // Optica Applicata : international scientific journal. - 2015. - Vol. XLV, No. 4. - P. 535-543.

The photothermoacoustic method has been used for diagnostics of thermobarodynamic processes in the metal In(400 nm)/semiconductor (CdTe) thin-film system under nanosecond laser irradiation (7 ns, λ = 532 nm) in natural conditions (in air) and in a liquid medium (water). From the analysis of the data obtained, the dependence of the pressure induced in the energy-release region on the irradiation energy density has been established and the melting threshold of In film has been determined. Under irradiation of In/CdTe in water, the pressure is higher than in air: 17 times higher at the melting threshold of In film and 30 times higher at twice the temperature. It has been found that the laser pulse treatment of In/CdTe/Au samples in water makes it possible to obtain diode structures with better parameters: smaller leak currents and a steeper current-voltage characteristic under the forward bias of the p - n junction.

Фототермоакустическим методом проведена диагностика термобародинамических процессов, происходящих при наносекундном лазерном облучении (7 ns, λ = 532 nm) в естественных условиях (на воздухе) и в жидкой среде (вода), тонкопленочной системы металл In(400 nm)−полупроводник CdTe. На основе анализа полученных данных установлена зависимость давления, возникающего в области энерговыделения, от плотности энергии облучения системы и определен порог плавления плeнки In. При облучении In/CdTe в воде давление больше, чем на воздухе — в 17 раз на пороге плавления плeнки In и в 30 раз при его двухкратном превышении. Выяснено, что импульсная лазерная обработка образцов In/CdTe/Au в воде позволяет получать диодные структуры с лучшими параметрами — меньшими токами утечки и более крутой вольтамперной характеристикой при прямом смещении p−n-перехода.

A gas discharge is observed in light-emitting diodes based on an InGaN/GaN structure for currents significantly greater than the operating currents, under conditions of considerable self-heating with formation of blisters in the polymer case of the LED, localized above the emitting surface of the heterostructure. In this case, we detected threshold appearance of intense emission in the red and infrared ranges of the spectrum. We show that the major mechanism for this emission is formation of a gas-discharge plasma as a result of non-oxidative thermal degradation of the polymer, surrounding the heterostructure and current carrying contacts.

In paper reveals reasons and mechanisms of fault of high power light-emitting diodes based on the GaN in the moment of switching (at the work voltage switch) due to melting of thin whisker contact based on the gold. Found out rapid degradation of high power light-emitting diodes at increasable constant direct currents.

The features of mass transfer of indium in high-resistance CdTe crystals under nanosecond irradiation of the In-CdTe structure by laser pulses have been studied and analyzed. The mass transfer coefficients are determined and the average transfer rate of the indium atoms in CdTe under irradiation is evaluated. It is assumed that the concentration diffusion of indium in CdTe and the transfer of impurity atoms by the front of the laser-induced shock wave are not dominant mechanisms of mass transfer under dynamic doping. The most probable process, which provides the formation of the inverse layer in the surface region of the CdTe crystal under nanosecond laser irradiation of the In film, is an transfer of interstitial In atoms due to the thermal fluctuation jumps under the action of the driving force of the thermoelastic stresses and temperature gradient.

The question of a relaxation of superficial mechanical pressure after a pulse laser irradiation in complex semiconductor compounds which is accompanied by formation of the difficult acoustic response is considered. In work it is shown, that the laser-induced melting threshold of single and poly- crystals can be established on dependence of amplitude and (or) energy of the acoustic response — the laser pulse intensity, in particular by the given method establishes melting thresholds of single crystals GaAs, CdTe and S³ at nanoseconds pulse irradiation of ruby and neodymium laser. It is established, that at nanoseconds laser pulse irradiation is possible registration only discrete highenergy acoustic emission due to a fast relaxation created elastic and thermoelastic pressure.

We present the results of of studies of the correlation of acoustic emission (AE) and reversible and irreversible changes of electrophysical characteristics of the light-emitting heterostructures on the basis of InGaN and GaAsP in the process of their degradation on the passage of the forward current with a critical density. It is established that the process of local rearrangement of a defective structure on the passage of a current, which is accompanied by AE, has thermoactivation character: with increase in the temperature, the AE occurence threshold decreases, and, at the same time, the number of active sources of AE grows. With decrease in the temperature, the AE occurence threshold approaches the destruction threshold. In this case, the processes of natural ageing considerable increase the thresholds of the AE occurence and the destruction of a structure.

The effect of a threshold process of surface melting on the acoustic response in CdTe and GaAs subjected to pulsed laser radiation is considered and the mechanisms of excitation of sonic signals are analyzed. Melting thresholds of the surface of binary compounds CdTe and GaAs are established under irradiation by pulses of nanosecond duration of ruby and neodymium lasers from measurements of the amplitude of the acoustic response.

In the A(3)B(5) heterostructures, the acoustic-emission occurrence, electrical noises and quantum yield fluctuations are shown to correlate in time and have the common origin.

For the first time it is shown, that the correlation in changes of electroluminescence spectrum and a threshold of origin of an acoustic emission in epitaxial lightdiode n(+)-n-p-structures GaP0.85As0.15 takes place. It is shown, that the density of a direct current of diode determines intensity of discrete acoustic emission, detrusion and redistribution of intensity in maximums of an electroluminescence spectrum, velocity and quantity of a degradation of emissive power.