UCLA researchers in the Department of Electrical & Computer Engineering have grown GaAs epitaxial films with high crystalline quality on alternative substrates.
Integrating compound semiconductors, such as gallium arsenide (GaAs), onto foreign substrates, such as silicon, enables high performance electronic and optoelectronic devices at a reduced cost. Using a cheap foreign substrate such as silicon reduces the amount of GaAs required during the device fabrication process. However, growing GaAs on alternative substrates yields epitaxial layers with poor crystalline quality and therefore devices with compromised performance. One alternative to these thin films is nanowire architectures, but the performance of GaAs nanowire devices grown on graphene remains limited by the nanowire geometry. Therefore, thin-layer devices with high performance can be achieved, but with additional processing methods.
UCLA researchers have grown GaAs epitaxial films with high crystalline quality on either graphene or silicon substrates. The growth method uses a buffer layer between the substrate and epitaxial film to mitigate the lattice and thermal expansion mismatch between GaAs and the underlying substrate. When using the buffer layer, the GaAs defect density grown on silicon substrates is lower than previous literature that uses either patterned or non-patterned growth. The buffer layer is compatible with typical device fabrication processes, and the additional steps are minimal. This technique for growing high crystal quality compound semiconductors can possibly be applied to other semiconductors such as gallium nitride.
epitaxial growth, buffer layer, crystalline quality, compound semiconductors, III-V materials, gallium arsenide, heterointegration, monolithic device, lattice mismatch