טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSteinberg Oren
SubjectGrowth and Characterization of the InP-based Multi-
Quantum Well Layers (MQW) for Optoelectronic
Applications
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Emil Zolotoyabko


Abstract

Indium phosphide (InP) and related compounds are key materials for optoelectronic devices used in optical fiber communication systems. Excellent semiconductor material quality is an essential requirement for fabrication of optoelectronic devices, their functionality being strongly dependent on the structural and geometrical parameters of the multilayers. In this research, a set of the InGaAsP multi-quantum well (MQW) layers with different well and barrier thicknesses, as well as different numbers of superlattice periods, was grown by metalorganic vapor phase epitaxy (MOVPE) and characterized by various experimental techniques such as HRXRD, PL, HRSEM and AFM. The structural and geometrical parameters of MQWs were determined by means of HRXRD measurements combined with advanced simulations of diffraction profiles. For this purpose, a novel simulation program (DIWAS) in the MATLAB format was used, which is based on the direct summation of waves scattered by individual atomic planes.
          It was found that the changes made in the multilayer structure did not practically affect rather low values of interface roughness and averaged d-spacing fluctuations, indicating high structural quality of the all grown MQW structures. Furthermore, the measured optical characteristics (PL signals) with only one exception showed an expected trend, i.e. higher PL peak intensity for thicker well layers and increasing number of QW periods. However, significant reduction of the PL signal, found in one of the samples, forced us to examine the surface morphology in grown structures by surface sensitive techniques, such as AFM and HRSEM. In fact, only in this specific sample both AFM and HRSEM revealed material discontinuities in a form of elliptic nano-pores about 200 nm in size. The visible density of these pores (surface coverage) is nearly 1 %.  Practically, the surface area of the defected material (around visible pores) can be even higher, increasing the fraction of non-radiative recombination and thus reducing the PL signal. The accomplished research confirmed that a set of experimental techniques, including HRXRD combined with DIWAS simulations, PL, AFM and HRSEM can be successfully used to completely characterize the quaternary semiconductor MQW structures