Flat metamorphic InAlAs buffer layer on GaAs(111)A misoriented substrates by growth kinetics control

We have successfully grown, through the detailed control of the growth kinetics, flat InAlAs metamorphic buffer layers on 2 degrees -off GaAs(111)A substrates using molecular beam epitaxy. Almost full plastic relaxation is obtained for a layer thickness > 40 nm. The control of an adatom diffusion length and a step ejection probability from the bunches permits a reduction of the InAlAs epilayer root-mean-square surface roughness to 0.55 nm

УПРУГОНАПРЯЖЕННЫЕ СЛОИ И НАНООСТРОВКИ GESISN В МНОГОСЛОЙНЫХ ПЕРИОДИЧЕСКИХ СТРУКТУРАХ

This work deals with elastically strained GeSiSn films and GeSiSn islands. Kinetic diagram of GeSiSn growth at different lattice mismatches between GeSiSn and Si has been established. Multilayer periodic structures with pseudomorphic GeSiSn layers and GeSiSn island array have been obtained. The density of the islands in the GeSiSn layer reaches 1.8 ⋅ 1012 cm−2 at an average island size of 4 nm. Analysis of the rocking curves showed that the structures contain smooth heterointerfaces, and strong changes of composition and thickness from period to period have not been found. Photoluminescence has been demonstrated and calculation of band diagram in the model solid theory approach has been carried out. Luminescence for the sample with pseudomorphic Ge0.315Si0.65Sn0.035 layers in narrow range of 0.71—0.82 eV is observed with the maximum intensity near 0.78 eV corresponding to a 1.59 µm wavelength. Based on a band diagram calculation for Si/ Ge0.315Si0.65Sn0.035/Si heterocomposition, one can conclud that luminescence with a photon energy of 0.78 eV corresponds to interband transitions between the X−valley in the Si and the heavy hole subband in the Ge0.315Si0.65Sn0.035 layer.Установлена кинетическая диаграмма морфологического состояния пленок GeSiSn при несоответствии параметров решетки между GeSiSn и Si от 3 до 5 %. На основе подбора толщины пленки GeSiSn выращены многослойные периодические структуры с псевдоморфными слоями и слоями, содержащими массив островков GeSiSn с плотностью до 1,8 ⋅ 1012 см−2 и средним размером 4 нм. Проведен анализ кривых дифракционного отражения для многослойных периодических структур. Показано наличие гладких гетерограниц, псевдоморфное состояние пленок GeSiSn и отсутствие изменений состава, а также толщины от периода к периоду. Получены спектры фотолюминесценции для структуры с псевдоморфными слоями Ge0,315Si0,65Sn0,035 с максимумом интенсивности фотолюминесценции вблизи 0,78 эВ, что соответствует длине волны 1,59 мкм. Проведен расчет зонной диаграммы с использованием подхода model solid theory. Исходя из результатов расчета зонной диаграммы, установлено, что обнаруженный пик люминесценции соответствует межзонным переходам между X−долиной в Si или между ∆4−долиной в Ge0,315Si0,65Sn0,035 и подзоной тяжелых дырок в слое Ge0,315Si0,65Sn0,035. Результаты исследований демонстрируют бездислокационные структуры с упругонапряженными псевдоморфными слоями и слоями, включающими массив островков высокой плотности. Дальнейшее изучение многослойных периодических структур будет направлено на увеличение содержания Sn и сравнение оптических свойств структур с островками и без островков

Telecom-wavelength InAs QDs with low fine structure splitting grown by droplet epitaxy on GaAs(111)A vicinal substrates

We present self-assembly of InAs/InAlAs quantum dots by the droplet epitaxy technique on vicinal GaAs(111)A substrates. The small miscut angle, while maintaining the symmetries imposed on the quantum dot from the surface, allows a fast growth rate thanks to the presence of preferential nucleation sites at the step edges. A 100 nm InAlAs metamorphic layer with In content ≥50% directly deposited on the GaAs substrate is already almost fully relaxed with a very flat surface. The quantum dots emit at the 1.3 μm telecom O-band with fine structure splitting as low as 16 μeV, thus making them suitable as photon sources in quantum communication networks using entangled photons

Growth of epitaxial SiSn films with high Sn content for IR converters

Growth of SiSn compounds with a Sn content from 10 to 35% is studied. The morphology and surface structure of the SiSn layers are examined and the kinetic diagram of the morphological state of SiSn films is established in the temperature range of 150–450°C. During the growth of SiSn films from 150 to 300°C, oscillations of specular beam were observed. For the first time, periodic multilayer SiSn/Si structures with pseudomorphic monocrystalline SiSn layers with the Sn content from 10 to 25% are grown. The c(8×4) and (5×1) superstructures are identified during the growth of Si on the SiSn layer and the conditions are determined for the formation of the desired Si surface structure by controlling the growth temperature. From the diffraction reflection curves, the lattice parameter, the SiSn composition, and the period in the multilayer periodic structure are defined, which with high precision correspond to the specified values

Morphology, structure, and optical properties of semiconductor films with GeSiSn nanoislands and strained layers

The dependences of the two-dimensional to three-dimensional growth (2D-3D) critical transition thickness on the composition for GeSiSn films with a fixed Ge content and Sn content from 0 to 16% at the growth temperature of 150 °С have been obtained. The phase diagrams of the superstructure change during the epitaxial growth of Sn on Si and on Ge(100) have been built. Using the phase diagram data, it becomes possible to identify the Sn cover on the Si surface and to control the Sn segregation on the superstructure observed on the reflection high-energy electron diffraction (RHEED) pattern. The multilayer structures with the GeSiSn pseudomorphic layers and island array of a density up to 1.8 × 1012 cm−2 have been grown with the considering of the Sn segregation suppression by the decrease of GeSiSn and Si growth temperature. The double-domain (10 × 1) superstructure related to the presence of Sn on the surface was first observed in the multilayer periodic structures during Si growth on the GeSiSn layer. The periodical GeSiSn/Si structures demonstrated the photoluminescence in the range of 0.6–0.85 eV corresponding to the wavelength range of 1.45–2 μm. The calculation of the band diagram for the structure with the pseudomorphic Ge0.315Si0.65Sn0.035 layers allows assuming that photoluminescence peaks correspond to the interband transitions between the X valley in Si or the Δ4-valley in GeSiSn and the subband of heavy holes in the GeSiSn layer

Synthesis of epitaxial films based on Ge-Si-Sn materials with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions

Results of investigations into the synthesis of heterostructures based on Ge–Si–Sn materials by the method of low-temperature molecular beam epitaxy are presented. The formation of epitaxial films during structure growth has been controlled by the reflection high-energy electron diffraction method. Films with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions are grown with Sn content changing from 2 to 10 % at temperatures in the interval 150–350°С. The stressed state, the composition, and the lattice parameter are studied by the x-ray diffraction method using Omega-scan curves and reciprocal space maps. A tensile strain in the Ge film during Ge/Ge0.9Sn0.1/Si structure growth has reached 0.86%

Synthesis of epitaxial films based on Ge-Si-Sn materials with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions

Results of investigations into the synthesis of heterostructures based on Ge–Si–Sn materials by the method of low-temperature molecular beam epitaxy are presented. The formation of epitaxial films during structure growth has been controlled by the reflection high-energy electron diffraction method. Films with Ge/GeSn, Ge/GeSiSn, and GeSn/GeSiSn heterojunctions are grown with Sn content changing from 2 to 10 % at temperatures in the interval 150–350°С. The stressed state, the composition, and the lattice parameter are studied by the x-ray diffraction method using Omega-scan curves and reciprocal space maps. A tensile strain in the Ge film during Ge/Ge0.9Sn0.1/Si structure growth has reached 0.86%

Growth of epitaxial SiSn films with high Sn content for IR converters

Growth of SiSn compounds with a Sn content from 10 to 35% is studied. The morphology and surface structure of the SiSn layers are examined and the kinetic diagram of the morphological state of SiSn films is established in the temperature range of 150–450°C. During the growth of SiSn films from 150 to 300°C, oscillations of specular beam were observed. For the first time, periodic multilayer SiSn/Si structures with pseudomorphic monocrystalline SiSn layers with the Sn content from 10 to 25% are grown. The c(8×4) and (5×1) superstructures are identified during the growth of Si on the SiSn layer and the conditions are determined for the formation of the desired Si surface structure by controlling the growth temperature. From the diffraction reflection curves, the lattice parameter, the SiSn composition, and the period in the multilayer periodic structure are defined, which with high precision correspond to the specified values

Elastically strained GeSiSn layers and GeSiSn islands in multilayered periodical structures

This work deals with elastically strained GeSiSn films and GeSiSn islands. The kinetic diagram of GeSiSn growth for different lattice mismatches between GeSiSn and Si has been drawn. The multilayered periodic structures with pseudomorphic GeSiSn layers and GeSiSn island arrays have been obtained. The density of the islands in the GeSiSn layer is 1.8 · 1012 cm-2 for an average island size of 4 nm. Analysis of the rocking curves has shown that the structures contain smooth heterointerfaces, and no abrupt changes of composition and thickness between periods have been found. Photoluminescence has been demonstrated and calculation of band diagram with the model-solid theory has been carried out. Luminescence presented for sample with pseudomorphic Ge0.315Si0.65Sn0.035 layers in the narrow range 0.71–0.82 eV is observed with the maximum intensity near 0.78 eV corresponding to 1.59 µm wavelength. Based on the band diagram calculation for Si/Ge0.315Si0.65Sn0.035/Si heterocomposition we have concluded that 0.78 eV photon energy luminescence corresponds to interband transitions between the X-valley in Si and the heavy hole subband in the Ge0.315Si0.65Sn0.035 layer