Stimulated emission and lasing in Cu(In,Ga)Se2 thin films

Stimulated emission and lasing in Cu(In,Ga)Se 2 thin films have been demonstrated at a temperature of 20 K using excitation by a nanosecond pulsed N 2 laser with power densities in the range from 2 to 100 kW cm − 2 . Sharp narrowing of the photoluminescence band, superlinear dependence of its intensity on excitation laser power, as well as stabilization of the spectral position and of the full-width at half-maximum of the band were observed in the films at increasing excitation intensity. The stimulated emission threshold was determined to be 20 kW cm − 2 . A gain value of 94 cm − 1 has been estimated using the variable stripe length method. Several sharp laser modes near 1.13 eV were observed above the laser threshold of I thr ~ 50 kW cm −

Stimulated emission and optical properties of solid solutions of Cu(In,Ga)Se2 direct band gap semiconductors

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of ~20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of ~20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films

Temperature dependence of AgIn13S20 single crystal band gap

AgIn13S20 single crystals were grown by the vertical Bridgman method. The grown crystals composition was determined by X-ray spectroscopy analysis; the crystal structure was determined by X-ray method. It was shown, that AgIn13S20 compound crystallize in the cubic spinel structure. The band gaps of the obtained single crystals were estimated from transmittance spectra in the temperature range of 10-320 K. The band gap values decreased with temperature

Photoluminescence, Stimulated and Laser Emission in CuInSe2crystals

Excitonic quality CuInSe2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nanosecond pulsed lasers at power densities from 0.01 to 76 kW/cm2. Increasing the excitation power density level to 26 kW/cm2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated on the top of the SE band, a structure of equidistant sharp lines attributed to laser emission. © 2021 Author(s).This work was supported by State Program of Scientific Research of the Republic of Belarus “Physical Material Science, New Materials and Technologies” (Project No. 1.4.4) and Belarusian Republican Foundation of Basic Research (Grant No. F20M-058). The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (“Spin” No. AAAA-A18-118020290104-2)

AlGaN/GaN high electron mobility transistor heterostructures grown by ammonia and combined plasma-assisted ammonia molecular beam epitaxy

The structural properties and surface morphology of AlN epitaxial layers grown by ammonia (NH3) and plasma-assisted (PA) molecular beam epitaxy (MBE) at different growth conditions on (0001) sapphire were investigated. The lowest RMS roughness of ~0.7 nm was achieved for the sample grown by NH3 MBE at a substrate temperature of 1085 °C and NH3 flow of 100 standard cm3 min−1. Atomic force microscopy measurements demonstrated a terrace-monolayer step-like surface morphology. Furthermore, the optimal substrate temperature for growth of GaN and AlGaN layers was determined from analysis of the GaN thermal decomposition rate. Using the optimized growth conditions, high electron mobility transistor heterostructures were grown by NH3 MBE on different types of AlN nucleation layer deposited by NH3 MBE or PA MBE. The grown heterostructures demonstrated comparable two-dimensional electron gas (2DEG) properties. The maximum 2DEG mobility of ~2000 cm2 V–1 s–1) at a 2DEG density of ~1.17 × 1013 cm−2 was achieved for the heterostructure with a PA MBE-grown AlN nucleation layer. The obtained results demonstrate the possibility of successful combination of different epitaxial approaches within a single growth process, which will contribute to the development of a new type of hybrid epitaxy that exploits the advantages of several technologies

Ultraviolet stimulated emission in AlGaN layers grown on sapphire substrates using ammonia and plasma-assisted molecular beam epitaxy

Ammonia and plasma‐assisted (PA) molecular beam epitaxy modes are used to grow AlN and AlGaN epitaxial layers on sapphire substrates. It is determined that the increase of thickness of AlN buffer layer grown by ammonia‐MBE from 0.32 μm to 1.25 μm results in the narrowing of 101 X‐Ray rocking curves whereas no clear effect on 002 X‐Ray rocking curve width is observed. It is shown that strong GaN decomposition during growth by ammonia‐MBE causes AlGaN surface roughening and compositional inhomogeneity, which leads to deterioration of its lasing properties. AlGaN layers grown by ammonia‐MBE at optimized temperature demonstrate stimulated emission (SE) peaked at λ = 330 nm, 323 nm, 303 nm and 297 nm with the SE threshold values of 0.7 MW cm−2, 1.1 MW cm−2, 1.4 MW cm−2 and 1.4 MW cm−2, respectively. In comparison to these, AlGaN layer grown using PA‐MBE pulsed modes (migration‐enhanced epitaxy, metal‐modulated epitaxy, and droplet elimination by thermal annealing) shows a SE with a relatively low threshold (0.8 MW cm−2) at the considerably shorter wavelength of λ = 267 nm

АММИАЧНАЯ МОЛЕКУЛЯРНО-ПУЧКОВАЯ ЭПИТАКСИЯ ГЕТЕРОСТРУКТУР AlGaN НА ПОДЛОЖКАХ САПФИРА

In order to develop a technology for the growth of Al(Ga)N-based heterostructures, the effect of different molecular beam epitaxy growth conditions on the properties of AlN and AlGaN layers was studied. The optimal conditions for the growth of AlN buffer layers were established, which made it possible to achieve a root mean square roughness as small as 0.7 nm. It was shown that an increase of AlN layer thickness leads to a decrease of density of edge dislocations, while no explicit dependence of the screw dislocation densityon the layer thickness was observed. The minimal obtained dislocations density values for 1.25μm-thick AlN layer were nedges = 5.9×109 cm-2 and nscrew = 2.2×107 cm-2 for edge and screw dislocations respectively. As a result of optimization of the AlGaN growth temperature, a series of 0.15μm-thick layers was grown, which showed stimulated emission at wavelengths λ = 330 nm, 323 nm, 303 nm, and 297 nm with threshold powerdensities of 0.7 MW/cm2, 1.1 MW/cm2, 1.4 MW/cm2 and 1.4 MW/cm2, respectively. The determined optimal epitaxy conditions for AlN and AlGaN layers were used to grow the AlGaN/GaN high electron mobility transistor structure on a sapphire substrate with two-dimensional electron gas, which had a mobility of 1950 cm2/(Vs) at a concentration of 1.15×1013 cm-2. The obtained results are important for creating of nitride-basedUV-emitting optoelectronic semiconductor devices, as well as high-power and high-frequency electronic devices.В работе с целью разработки технологии роста гетероструктур на основе Al(Ga)Nисследовалось влияние различных условий роста гетероструктур молекулярно-пучковой эпитаксией на свойства слоев AlN и AlGaN. Были установлены условия для роста буферных слоев AlN, которые позволили достигнуть среднеквадратичного значения величины шероховатостей 0,7 нм. Показано, что увеличение толщины слоя AlN приводит к уменьшению плотности краевых дислокаций, в то время как явной зависимости плотности винтовых дислокаций от толщины слоя не наблюдалось. Минимальные полученные значения плотности проникающих дислокаций для слоя AlN толщиной 1,25 мкм составили nкраев. = 5,9×109 см-2 и nвинт. = 2,2×107 см-2. В результате оптимизации температуры роста AlGaN была выращена серия слоев толщиной 0,15 мкм, показавших стимулированное излучение на длинах волн λ = 330 нм, 323 нм, 303 нм и 297 нм с пороговыми плотностями мощности 0,7 МВт/см2, 1,1 МВт/см2, 1,4 МВт/см2 и 1,4 МВт/см2 соответственно. Установленные условия эпитаксии слоев AlN и AlGaN на подложках сапфира были использованы для роста транзисторной структуры AlGaN/GaN на подложке сапфира с двумерным электронным газом, который имел подвижность 1950 см2/(Вс) при концентрации 1,15×1013 см-2. Полученные результаты важны для создания излучающих оптоэлектронных полупроводниковых приборов, работающих в УФ области спектра, а также приборов силовой и высокочастотной электроники на основе нитридов

AMMONIA MOLECULAR BEAM EPITAXY OF AlGaN HETEROSTRUCTURES ON SAPPHIRE SUBSTRATES

In order to develop a technology for the growth of Al(Ga)N-based heterostructures, the effect of different molecular beam epitaxy growth conditions on the properties of AlN and AlGaN layers was studied. The optimal conditions for the growth of AlN buffer layers were established, which made it possible to achieve a root mean square roughness as small as 0.7 nm. It was shown that an increase of AlN layer thickness leads to a decrease of density of edge dislocations, while no explicit dependence of the screw dislocation densityon the layer thickness was observed. The minimal obtained dislocations density values for 1.25μm-thick AlN layer were nedges = 5.9×109 cm-2 and nscrew = 2.2×107 cm-2 for edge and screw dislocations respectively. As a result of optimization of the AlGaN growth temperature, a series of 0.15μm-thick layers was grown, which showed stimulated emission at wavelengths λ = 330 nm, 323 nm, 303 nm, and 297 nm with threshold powerdensities of 0.7 MW/cm2, 1.1 MW/cm2, 1.4 MW/cm2 and 1.4 MW/cm2, respectively. The determined optimal epitaxy conditions for AlN and AlGaN layers were used to grow the AlGaN/GaN high electron mobility transistor structure on a sapphire substrate with two-dimensional electron gas, which had a mobility of 1950 cm2/(Vs) at a concentration of 1.15×1013 cm-2. The obtained results are important for creating of nitride-basedUV-emitting optoelectronic semiconductor devices, as well as high-power and high-frequency electronic devices

Photoluminescence, stimulated and laser emission in CuInSe2 crystals

Excitonic quality CuInSe2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nanosecond pulsed lasers at power densities from 0.01 kW/cm2 to 76 kW/cm2 . Increasing the excitation power density level to 26 kW/cm2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated on the top of the SE band a structure of equidistant sharp lines attributed to laser emission. at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated a structure of equidistant sharp lines attributed to laser emission on the top of the SE band. The lasing regime suggests the presence of volumes with parallel faces (microcracks or grain boundaries), which act as laser mirrors within the CuInSe2 crystals

Temperature dependence of the band gap of AgIn8S12.5 single crystals

Вертикальным методом Бриджмена выращены монокристаллы AgIn8S12.5. Методом рентгеноспектрального анализа определен состав полученных монокристаллов, методом рентгеновской дифракции — кристаллическая структура. Показано, что выращенные монокристаллы кристаллизуются в кубической структуре шпинели. По спектрам пропускания в интервале температур 10 − 320 K определена ширина запрещенной зоны, которая с понижением температуры возрастает. AgIn 8 S 12.5 single crystals were grown by the vertical Bridgman method. The composition of the single crystals was determined by the X-ray spectral analysis method, and the crystal structure was determined by the X-ray diffraction method. It is shown that the grown single crystals crystallized in the cubic spinel structure. Transmittance spectra in the temperature range 10 − 320 K were used to determine the band gap of the crystals, which increased with decreasing the temperature