Terahertz Emission Enhancement of i-/n-Gallium Arsenide Thin Film on a Porous Silicon Distributed Bragg Reflector designed at 800nm

A semiconductor terahertz (THz) emitter based on an active i-/n-GaAs layer integrated on a porous silicon (PSi) distributed Bragg reflector (PSi-DBR) is presented. It is specifically designed for the use of a very thin GaAs film of thickness less than the penetration depth of the 800nm laser beam $(\sim 1\mu \mathrm{m})$ . The DBR acts as a reflecting substrate for the excess transmitted photoexcitation. Using a 550nm-thick GaAs, the novel design exhibited a 67% increase in peak-to peak THz signal compared to a similar GaAs on silicon (Si) substrate. The enhancement can be attributed to the increased optical absorption and multiple reflections in the active layer.