Concentration-Dependent Photoluminescence and Raman of p-Type GaAs Grown in a Metallic-Arsenic-Based-MOCVD System

This work presents the optical and structural characterization of p-type GaAs epilayers. The gallium precursor was the organometallic compound trimethylgallium (TMG). The influence of the doping in the optical and structural properties of the GaAs layers has been studied by photoluminescence (PL) and Raman dispersion measurements. The range of analyzed hole concentration was from 1017 to 1019 cm-3 as measured by the Hall-van der Pauw method. For carrying out doping p-type, it was necessary to modify the hydrogen activity in the growth atmosphere with the control of a H2+N2 mixture, which was used like transporting gas. The photoluminescence response and Raman dispersion of the layers are strongly dependence of the growth temperature, which were investigated based on the hole concentration. The PL response of the layers shows two radiative transitions, band-to-band and band-to-C-acceptor at low hole concentration and disappears at high concentrations. Raman scattering spectra show LO mode at 270 cm-1 for low doped samples and a LO-like mode at 290 cm-1 produced by the phonon-holeplasmon coupling for high doped samples.