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The methods of high-resolution X-ray diffraction have been used to study the multilayered structures in an InGaN/GaN system grown by the method of metal-organic chemical-vapor deposition. A correlation between the strain state (relaxation) of the system, the indium content within quantum wells, the ratio of the barrier/well thicknesses, and the number of quantum wells in the active superlattice is established. It is shown that partial relaxation is observed even in a structure with one quantum well. The results we obtained indicate that the relaxation processes are bound to appreciably affect the optical characteristics of devices. [ABSTRACT FROM AUTHOR]

Studies the dependence of the chirp parameter on heavy- and light-hole energy splitting in InGaAs/InAlAs p-i-n multiple quantum well structures. Analysis of the change in the absorption curve of different multiple quantum well structures.

Amplitude modulators are basic devices for long distance optical communication. Their development started using the electro-absorption of bulk material, called the Franz–Keldysh effect. High frequency applications required larger absorption changes with electric field, therefore, attention has been shifted to multiple quantum well structures where the quantum confined Stark effect (QCSE) could improve device performance at high bit rates. However, if the amplitude modulators based on the QCSE are expected to be used in the next multigigabit long-haul fiber transmission systems, the multiple quantum well structure should be optimized taking into consideration parameters such as insertion loss, contrast ratio, chirp, polarization independence, operation voltage and wavelength. Much work has been done in several III–V semiconductor systems. The results of a detailed optimization for InGaAs/InAlAs multiple quantum well structures are presented, as an example. [Copyright &y& Elsevier]

The influence of strain and barrier/well thickness ratio on recombination processes in multi-quantum well (MQW) Al 0.1 Ga 0.9 N/GaN structures was investigated using X-ray diffraction and Raman and photoluminescence spectroscopies. The deformation state of the wells and barriers was determined. In addition, the value of the polarization fields, the density of polarization charges, and the positions of energy levels for optical transitions within the quantum wells were calculated. It was established that compressive strain in the buffer layer as well as in the layers of the MQWs with respect to the buffer layer lead to the piezoelectric fields having equal sign in the well and the barrier. As a result, the recombination of donor–acceptor pairs dominates over transitions between electron and hole states in the quantum well. [ABSTRACT FROM AUTHOR]