Comparison of terahertz radiation and hot-electron dynamics in CdTe and GaAs photoconductive antennas excited at 520 nm

Abstract

Photoconductive antennas (PCAs) remain a cornerstone for efficient terahertz (THz) generation. Given the recent proliferation of ytterbium (Yb) laser technology, adapting PCAs to these specific laser characteristics is essential. In this work, we investigate the THz emission of typical dipole-type semi-insulating gallium arsenide (SI GaAs) and cadmium telluride (CdTe) PCAs with a 30 μm gap, driven by the second harmonic (520 nm) of an Yb-based femtosecond oscillator laser. We demonstrate that, with optimized bias and optical excitation, CdTe PCA can generate a peak-to-peak THz field 53% larger than that of GaAs. While GaAs initially exhibits higher emission at low fields, the ability of the CdTe PCA to sustain higher bias fields at high optical power without catastrophic failure is an advantage that leads to the generation of higher THz fields. Furthermore, we highlight fundamental differences in hot-electron dynamics between the two semiconductors. Disparities in intervalley scattering rates, which govern carrier mobility and the resulting space-charge screening regime, lead to markedly different evolutions of the THz waveforms in GaAs vs CdTe. These findings establish CdTe as a robust alternative for high-power THz applications driven by Yb-based laser systems.