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Elastically strained supermultiperiod (100–1000 periods) AlGaAs/GaAs superlattices with different doping levels and slightly differing period thicknesses have been investigated. The proposed technique of characterization consisting of combined application of deep X-ray reflectometry based on a rigorous calculation method, as well as the well-known method of high-resolution X-ray reflectometry, has made it possible to investigate 100-period structures with 2-nm-wide Al0.3Ga0.7As barriers and 10-nm-wide GaAs wells and determine with a high accuracy the layer thicknesses and spread of interfaces. This achievement can be considered as a first step in further analysis of thick structures using bright synchrotron radiation source. The difference between the expected and obtained by the proposed method layer thicknesses is several percent, including that for samples with a high doping level (up to 1018 cm–3). All supermultiperiod structures are characterized by sharp interfaces with a standard deviation of about 0.1 nm. Based on the obtained data on the thicknesses, one can accurately determine the layer compositions using high-resolution X-ray diffraction. [ABSTRACT FROM AUTHOR]

Heterostructures with strongly-coupled multiple quantum wells, such as super-multiperiod superlattices with high perfection, may contain hundreds of layers, whose thicknesses can vary by orders of magnitude. The proposed method of characterization, consisting of the matched application of high-resolution X-ray diffractometry and reflectometry, makes it possible to study super-multiperiod structures of various types, including those with long periods and thin layers, and with high accuracy to determine the thicknesses of layers and roughness/diffuseness of boundaries. The difference between the expected and resulting thicknesses of the layers was 2–7% and 1–3% for the type I (InAs/GaAs) and type II (GaAs/Al0.3Ga0.7As) samples, respectively. Both types of structures are characterized by sharp interfaces with the RMS width of the transition layers of the order of several Å. Based on the best solution of inverse scattering problems, it is possible to determine with high accuracy both the morphology of the layers and their composition. That can be considered as the first step in the analysis of structures with a very large number of periods. [ABSTRACT FROM AUTHOR]

Promising semiconductor devices, such as quantum-cascade lasers and similar to them heterostructures with multiple strongly-coupled quantum wells, may contain hundreds and even thousands of layers. Independent methods of photoluminescence (PL) and transmission electron microscopy (TEM), along with X-ray diffractometry and reflectometry, make it possible to characterize super-multiperiod (SMP—superlattices with 100 and more periods) structures and to determine, with high accuracy, the thicknesses of layers, the roughness/diffusion of interfaces and the composition of solid solutions. The difference between the expected and measured using PL and TEM thicknesses of the layers of GaAs/AlGaAs samples synthesized by molecular beam epitaxy was 5–10%. The SMP structures are characterized by stable thicknesses of the layers in depth and sharp boundaries with a width of transition interfaces of the order of several Å that is consistent with the X-ray analysis. Based on the data obtained on thicknesses of layers, by comparing the theoretical and experimental values of photoluminescence intensities it is possible to accurately determine the composition of Al0.3Ga0.7As which corresponds to the X-ray diffraction data. [ABSTRACT FROM AUTHOR]

Studies of the properties of InGaAsN compounds and methods of controlling the emission wavelength in InAs/GaAsN/InGaAsN heterostructures grown by molecular beam epitaxy on GaAs substrates are reviewed. The results for different types of heterostructures with quantum-size InGaAsN layers are presented. Among those are (1) traditional InGaAsN quantum wells in a GaAs matrix, (2) InAs quantum dots embedded in an (In)GaAsN layer, and (3) strain-compensated superlattices InAs/GaAsN/InGaAsN with quantum wells and quantum dots. The methods used in the study allow controllable variations in the emission wavelength over the telecommunication range from 1.3 to 1.76 μm at room temperature. [ABSTRACT FROM AUTHOR]