Layer-engineered interlayer excitons

Photoluminescence (PL) from excitons serves as a powerful tool to characterize the optoelectronic property and band structure of semiconductors, especially for atomically thin two-dimensional transition metal dichalcogenide (TMD) materials. However, PL quenches quickly when the thickness of TMD materials increases from monolayer to a few layers, due to the change from direct to indirect band transition. Here, we show that PL can be recovered by engineering multilayer heterostructures, with the band transition reserved to be a direct type. We report emission from layer-engineered interlayer excitons from these multilayer heterostructures. Moreover, as desired for valleytronics devices, the lifetime, valley polarization, and valley lifetime of the generated interlayer excitons can all be substantially improved as compared with that in the monolayer-monolayer heterostructure. Our results pave the way for controlling the properties of interlayer excitons by layer engineering.

Equipment for growing semiconductor heterostructures in outer space

This article describes the features of the equipment developed at the Rzhanov Institute of Semiconductor Physics for conducting experiments on growing semiconductor heterostructures from molecular beams in outer space under the conditions of an orbital flight of the International Space Station. Working out the processes of epitaxy of semiconductor films in outer space will allow us to grow complex semiconductor structures with sharp boundaries, which serve as the basis for the creation of solar cells, as well as devices of modern microwave, optoand microelectronics. Cascade photovoltaic converters based on such multilayer heterostructures of A3B5 semiconductor compounds have high efficiency and radiation resistance and, therefore, are most widely used for the manufacture of space solar cells. The high efficiency of such batteries is due to the wide spectral range in which solar radiation is effectively absorbed and used in photovoltaic conversion.

МОДЕЛИРОВАНИЕ И РАСЧЕТ СПЕКТРА ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУРЫ С КВАНТОВОЙ ЯМОЙ НА ПРИМЕРЕ ALGaAS/GaAS

This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

МОДЕЛИРОВАНИЕ И РАСЧЕТ СПЕКТРА ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУРЫ С КВАНТОВОЙ ЯМОЙ НА ПРИМЕРЕ ALGaAS/GaAS

This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

Multilayer Heterostructures with Embedded CrSi2 and β-FeSi2 Nanocrystals on Si(111) Substrate: From the Formation to Photoelectric Properties

The studies are devoted to the development of the technology of multilayer incorporation of nanocrystals (NCs) of semiconductor chromium and iron disilicides with a layer density no less than 2x1010 cm-2, the establishment of the growth mechanism of heterostructures with two types of NCs, the determination of their crystalline quality and optical properties, as well as the creation and study of rectification and photoelectric properties of p-i-n diodes based on them. Morphologically smooth heterostructures with 6 embedded layers of CrSi2 nanocrystals and two types of embedded nanocrystals (with 4 layers of CrSi2 NCs and 2 layers of β-FeSi2 NCs) for optical studies and built-in silicon p-i-n diodes were grown for the first time. The possibility of optical identification of interband transitions in embedded nanocrystals in the photon energy range of 1.2 - 2.5 eV was determined from the reflection spectra and the strongest peaks in reflection from the integrated nanocrystals were determined: 2.0 eV for CrSi2 NCs and 1.75 eV for β-FeSi2 NCs. The created p-i-n diodes have a contact potential difference of 0.95 V, regardless of the type of embedded NCs. At 80 K, an absorption band (0.7 - 1.1 eV) was detected in the diodes, which was associated with carrier photo generation in the embedded CrSi2 and β-FeSi2 NCs. From the spectra of the photoresponse at 80 K, the band gap widths in the NCs were determined: 0.50 eV in CrSi2 and 0.70 eV in the superposition of the CrSi2 and β-FeSi2 NCs.