Growth Evaluation of Wafer-based Au-catalyzed GaAs Nanowires on GaAs(111)B Substrates with Different Patterning Conditions using µ-Raman Characterization

We report the relation between the catalyst patterning conditions and the intensity of the 1^st order Raman active modes in Au-catalyzed GaAs nanowires. Au-patterned GaAs(111)B substrates were prepared by e-beam Litho with varying patterning conditions and GaAs NWs were grown via VLS process using a solid-source MBE. To understand the effects of the preparation conditions and resulting morphologies on the optical characteristics of 1^st order TO and LO phonon modes of GaAs, the NWs were characterized by µ-Raman and SEM as a function of the e-beam dose rate, inter-dot spacing, and pattern size. The Ensembles of single crystalline NWs covered with different Au-thickness showed a downshift and asymmetric broadening of the TO and LO phonon peaks relative to GaAs bulk modes. The TO and LO intensity were clearly increased as well as the relatively higher peak shift and broadening of Raman spectra from the 100 nm pattern in response to the dose rate change. We have shown that not only the identifications of the changes in GaAs LO and Arsenic anti-site peaks are good indicators to characterize the quality of as-grown GaAs NWs but Raman spectroscopy is a powerful tool for characterizing chemical, structural, and morphological information of as-grown NWs within the supporting substrate.