Doping profiles of n-type GaAs layers grown on Si by the conformal method
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Doping profiles of n-type GaAs layers grown on Si by the conformal method Angel M. Ardila1,2, O. Martínez2, M. Avella2, J. Jiménez2, B. Gérard3, J. Napierala4 and E. GilLafon4 1 Depto. De Física, Facultad de Ciencias, Universidad Nacional de Colombia, Ciudad Universitaria, Santa Fe de Bogotá, Colombia 2 Física de la Materia Condensada, Facultad de Ciencias, Universidad de Valladolid, Valladolid, 47011, Spain 3 THALES, Corporate Research Laboratory, 91404 Orsay Cedex, France 4 LASMEA UMR CNRS 6602, Université Blaise Pascal, Les Cézeaux, 63177 Aubiére Cedex, France ABSTRACT We study doping profiles in selectively Si-doped GaAs layers grown by the conformal method. This growth technique allows to obtain GaAs/Si with optoelectronic quality. The samples are laterally grown, and selective doping with Si is carried out in such a way that doped stripes are intercalated with undoped ones. The study of the doping profiles was carried out by cathodoluminescence (CL) and micro-Raman (µR) spectroscopy. Abrupt doping profiles between doped and undoped stripes were demonstrated by monochromatic CL images. Deep level related CL bands can be observed between 1000 and 1400 nm, evidencing the complex mechanism for Si incorporation at the growth temperature (730 °C). Net doping concentrations and mobilities across the layers were determined from the analysis of the phonon-plasmon coupled modes in the µR spectra obtained with a lateral resolution better than 1 µm. INTRODUCTION Matching gallium arsenide to silicon, which currently shows up in special applications, that combine the low-cost robustness of silicon with the higher optoelectronic performance of the gallium arsenide, has been a technological goal for many years [1-5 ]. For example, this development could permit the integration of optical components like solid state lasers with the conventional electronic devices in the same chip, enabling on-chip and chip-to-chip optical interconnects; the design of new wireless devices, like radar systems that would help automobiles avoid collisions, and new semiconductor-based lighting systems. However, the obtention of defect free epilayers is subjected to some problems because of the large lattice (4%) and thermal (55%) mismatches between Si and GaAs, as well as the difficulties of growing a polar semiconductor on a non-polar one. Nowadays, important achievements were got using different deposition techniques and treatments (annealing[2], buffering layers in vertical growth[3], or passivating layers in lateral growth[4]). In spite of this, the density of crystal defects remains high enough to render unsuitable these layers for reliable optoelectronic applications. Pribat el al. [5,6] proposed an effective method to produce GaAs layers on Si substrates that consists of a lateral epitaxial growth on the sidewall of a GaAs seed stripe previously deposited on a Si substrate. We present in this paper the study of doping profiles in selectively Si-doped GaAs layers grown by the conformal method, using optical techniques. The carried out measurem
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