Terahertz photoconductive switch from GaAs grown on Ge substrate

This paper presents the fabrication and characterization of photoconductive terahertz switches based on GaAs epitaxial layers grown directly on centrosymmetric germanium substrates. The study aims to overcome the bandwidth limitations of conventional GaAs-based switches by leveraging the broader THz transmission of Ge. The authors investigate the influence of GaAs layer thickness on device performance, including breakdown fields, dark currents, and emitted THz spectra. The results demonstrate the potential of GaAs/Ge devices for broadband THz generation, despite certain challenges. The paper also discusses the unforeseen charge transport phenomena observed in these devices, which may provide insights for future optimizations.