Physical property analysis of C-doped GaAs as function of the carrier concentration grown by MOCVD using elemental arsenic as precursor

Abstract
This work presents the characterization of GaAs layers grown in a metallic-arsenic-based-MOCVD system. The gallium precursor was the compound trimethylgallium (TMG) and elemental arsenic as precursor of arsenic. The most important parameters of the growth process include the substrate temperature and the composition of the carrier gas; an gas mixture. The influence of carbon doping on the optical and electrical properties of GaAs layers have been studied by photoluminescence (PL) spectroscopy, Photoreflectance (PR) and Hall Effect measurements. To carry out doping with carbon in the range of around 10¹⁶ to 10²⁰ cm^-3, it was necessary to modifying the hydrogen activity in the reacting atmosphere with the control of the N₂+H₂, mixture which was used as carrier gas. The PL response of the samples is strongly dependent on the growth temperature and showed mainly two radiative transitions, band-to-band and band-to C-acceptor. PR spectra present transitions associated to GaAs. Besides, short period oscillations near the GaAs band-gap energy are observed, interpreted as Franz-Keldysh oscillations associated to the hole-ionized acceptor (h-A^-) pair modulations. For investigating the chemical bonds of impurity-related species in the GaAs layers optical absorption was measured using a FT-IR spectrometer. Device quality GaAs layers have been grown in a broad range of growth temperatures.