Terahertz emission of a 550nm-thick epitaxially lifted-off gallium arsenide thin film integrated on a porous silicon distributed Bragg reflector

The THz emission of an undoped/n-type GaAs thin film on a porous silicon distributed Bragg reflector (PSi DBR) is presented. The process was carried out by epitaxial lift-off of an MBE-grown GaAs epilayer, followed by integration on the DBR via Van der Waal's bonding. The active GaAs film has a total thickness less than the penetration depth of the 800 nm excitation source, while the PSi DBR substrate was designed as a reflector for the transmitted optical excitation photons at the film-substrate interface. The design exhibited a 67% increase in the peak-to-peak THz amplitude compared to a similar GaAs film integrated on silicon (Si) substrate. The THz enhancement was attributed to a higher number of photogenerated carriers in the film due to the increased 800nm light absorption and the additional drift-related THz radiation at the GaAs-PSi DBR interface.