Multilayer stacking and metal deposition effects on large area graphene on GaAs

Graphene was grown on copper and repeatedly transferred onto a GaAs semi-insulating substrate to form multilayers (1-10). These manually stacked graphene layers resulted in appreciable local variations of optical properties due to the local differences of stacking orders. In addition, most of the observed 2D/G intensity and area ratios of an n-multilayer CVD graphene is consistent with the characteristics of a single layer repeated n-times. However, multilayer graphene has many kinds of advantages for applications to optoelectronic devices. First, the G band shift is not related to the stacking order, proving that multilayer graphene reduces doping and strain effect from the substrate, which is confirmed by Raman results after metal electrode deposition. Second, the sheet resistance decreases with increasing number of layers and after thermal annealing. Another benefit of multilayer graphene is that each layer can be annealed after transfer, which greatly improves the sheet resistance and its lateral uniformity without intentional doping. We therefore conclude that multilayer CVD graphene is a good candidate for various GaAs-based electrical applications and its good electrical uniformity allows fabrication of devices on large scales.