Investigation on the interface electric field of aluminum-doped zinc oxide/p-type gallium arsenide (AZO/p-GaAs) heterojunctions for terahertz emission applications
Aluminum-doped zinc oxide (AZO) films were deposited on p-type GaAs substrates with different Al% via spray pyrolysis to investigate the dependence of terahertz (THz) emission on the interface electric field of AZO/p-GaAs heterostructures. Photoreflectance spectroscopy was used to measure the electric field at the interface of the heterojunctions. Reflection-geometry THz time-domain spectroscopy showed that the THz intensity gradually increases with Al doping and peaks at 2% Al, which coincides with the maximum electric field. Comparison of THz intensity and electric field confirms that the THz emission in AZO/p-GaAs is governed by photocarrier drift. In addition, it was shown that photocarrier drift is a dominant factor in the observed THz intensity enhancement.