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The present work presents the influence of the growth parameters on the structural and optical properties of undoped GaAsN epilayers and triple quantum wells 3×InGaAsN/GaAs obtained by atmospheric pressure metal organic vapour phase epitaxy APMOVPE. The structures were examined using high resolution X-Ray diffraction HRXRD, contactless electroreflectance CER, photocurrent PC and Raman RS spectroscopies. The influence of the growth temperature and the gas phase composition on the material quality and alloy composition of the investigated structures as well as the growth and calibration characteristics are presented and discussed. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Micro-Raman spectra taken from beveled p-GaAs samples covering a range of concentrations (1×1018–2×1019 cm−3) have been studied. This study concentrated on the evaluation of the changes of Raman intensities measured in frequency positions of transversal optical and longitudinal optical phonons along the bevel. These changes are dependent on doping concentration and due to this fact we have extracted a calibration function, which will be used to determine the doping concentration in nanometer-thin layers. There are two physical values, which was derived from this study: width of surface-depletion layer and width of space-charge layer. Good correspondence between experimental results and theoretical calculations is the proof of correctness of the model of explanation of the changes of micro-Raman and their analysis. The chemical procedure for preparation of homogeneous oxide-free bevel-shaped p-type GaAs structures with small angle was also developed. [Copyright &y& Elsevier]

Abstract: Micro-Raman spectroscopy was used to characterize beveled Zn delta (δ)-doped GaAs structures. By adapting procedures previously developed for the study of Si δ-doped GaAs structures, Zn-doping profiles were obtained for a set of structures prepared with different doping levels. Values of the doping spike concentration and the full-width at half-maximum of the doping profile were compared with the values obtained by the electrochemical capacitance–voltage (EC–V) and secondary ion mass spectroscopy (SIMS) methods. The good correspondence between this Raman procedure and other well-known methods proves the validity of the technique for determining doping profiles in Zn δ-doped GaAs structures. [Copyright &y& Elsevier]

Abstract: As CMOS is approaching the 22nm node, the importance of high-mobility materials such as Ge and GaAs is rapidly increasing. For the timely development of these new technologies accurate dopant and carrier-profiling solutions for source-drain extensions with these materials are required. Identical n-type-doped (Si, Se) layers on same and opposite type medium-doped layers on S.I. GaAs substrates will be investigated, with layer thicknesses ranging from 200 down to 50nm and doping concentration levels up to 1e20at/cm3. In this work, secondary ion mass spectrometry will be used for dopant profiling. For GaAs carrier profiling, conventional spreading resistance probe, as commonly used in Si-CMOS, fails. Hence, reliable alternatives need to be found for characterizing these high–low structures. Techniques to be discussed range from the more conventional approaches such as Hall or electrochemical capacitance–voltage (performed by different laboratories), over micro-Raman spectroscopy and photo-luminescence along a beveled surface, up to more advanced approaches using scanning spreading resistance microscopy. [Copyright &y& Elsevier]

Abstract: As CMOS is approaching the 22nm node, the importance of high-mobility materials such as Ge and GaAs is rapidly increasing. For the timely development of these new technologies accurate dopant and carrier-profiling solutions for source-drain extensions with these materials are required. Identical n-type-doped (Si, Se) layers on same and opposite type medium-doped layers on S.I. GaAs substrates will be investigated, with layer thicknesses ranging from 200 down to 50nm and doping concentration levels up to 1e20at/cm3. In this work, secondary ion mass spectrometry will be used for dopant profiling. For GaAs carrier profiling, conventional spreading resistance probe, as commonly used in Si-CMOS, fails. Hence, reliable alternatives need to be found for characterizing these high–low structures. Techniques to be discussed range from the more conventional approaches such as Hall or electrochemical capacitance–voltage (performed by different laboratories), over micro-Raman spectroscopy and photo-luminescence along a beveled surface, up to more advanced approaches using scanning spreading resistance microscopy. [Copyright &y& Elsevier]

Abstract: The generation and properties of photoexcited steady-state plasma of electrons and holes in bevel-shaped p-type GaAs structures were studied by micro-Raman spectroscopy. The best correspondence of theoretical calculations with experimental spectra was obtained by using of photoexcited carrier concentration of 1.1×1017 cm−3 and mobility 600 and 40cm2/Vs for the photoexcited steady-state electrons and holes, respectively. The analysis of the plasma behavior and its coupling with longitudinal optical phonons at different positions along the bevel shows that the mode resulting from this coupling causes the changes of Raman intensities recorded in frequency positions of transversal (TO) and longitudinal (LO) optical phonon peaks. These changes were further studied and physical interpretation was provided. The dependence of their ratio in the region affected by surface depletion layer can be fitted by linear function very well. The linearity was observed at all studied structures. This behavior on beveled structures prepared by special treatment with very low bevel angle can be used for analysis of the p-type GaAs nanostructures, particularly for measurement and extraction of a doping profile of p-type impurities in GaAs with very high resolution in nm scale. [Copyright &y& Elsevier]

Abstract: We present a new method of determining the depth profile of the doping concentration in Si δ-doped GaAs layers and GaAs-based heterostructures by micro-Raman spectroscopy. In-depth resolution is obtained by scanning the laser spot along a shallow bevel synthesized in the structure of interest. The doping level is determined by assessing changes in the ratio of the transversal to the longitudinal optical phonon lines intensities. The determined doping concentration values are in good agreement with those determined by secondary ion mass spectroscopy and capacitance–voltage methods. [Copyright &y& Elsevier]

Abstract: A new method for determining the doping concentrations in very thin GaAs layers is presented. The method is based on the evaluation and calibration of the changes in ratio of transversal to longitudinal optical phonon intensities measured by micro-Raman spectroscopy at different positions along the bevel prepared through the examined structure. The doping concentrations measurements by micro-Raman spectroscopy on bevelled structures are in good agreement with SIMS depth profiling analysis. [Copyright &y& Elsevier]

Si δ-doped GaAs layers were studied by micro-Raman spectroscopy. The spectra were recorded along the bevelled structure using the light of Ar+-ion laser (514.5 nm line) with high power density. The observed changes in the Raman spectra are discussed in the sense of coupling present between LO phonon and photoexcited electron–hole plasma and plasma of electrons arising from ionised Si atoms. Plasmon-LO-Phonon modes of the coupling of photoexcited plasma in δ-doped GaAs layers were observed for the first time. The minimal thickness of cap layer was estimated in the range of 10–19 nm depending on the doping concentration. [Copyright &y& Elsevier]