Abstract-Ion-Beam Modified Terahertz GaAs photoconductive antenna

Caiming Sun,

https://www.intechopen.com/online-first/ion-beam-modified-terahertz-gaas-photoconductive-antenna

Ion-implanted photoconductive GaAs terahertz (THz) antennas were demonstrated to deliver both high-efficiency and high-power THz emitters, which are attributed to excellent carrier acceleration and fast carrier trapping for THz generations by analyzing ultrafast carrier dynamics at subpicosecond scale. The implantation distance at over 2.5 μm is deep enough to make defects (Ga vacancies, AsGa+…, etc.) quite few; hence, a few with good mobility similar to bare GaAs ensures excellent carrier acceleration in shallow distance <1.0 μm as photo carriers are generated by the pump laser. The implantation dosage is carefully optimized to make carrier trapping very fast, and screen effects by photo-generated carriers are significantly suppressed, which increases the THz radiation power of SI-GaAs antennas by two orders of magnitude. Under the same photo-excitation conditions (pump laser power, bias voltage), photocurrents from GaAs antennas with optimum conditions 300 keV, 5 × 1014 cm−2 for H implantation are decreased by two orders of magnitude; meanwhile, the THz radiation is enhanced by over four times, which means that the electrical-to-THz power conversion efficiency is improved by a factor of over 1600.

Abstract-Efficient terahertz generation from lightly ion-beam-treated semi-insulating GaAs photoconductive antennas

Caiming Sun,  Aidong Zhang,

http://iopscience.iop.org/article/10.7567/APEX.10.102202

An ion beam technique is used to lightly treat semi-insulating GaAs terahertz (THz) photoconductive antennas (PCAs), and a novel structure with two layers, a carrier acceleration layer and a carrier trapping layer, is demonstrated to afford high-efficiency, high-power THz emitters. The key roles of vacancy defects produced by the ion beam in efficient THz generation are systematically described. The peak distribution of defects at approximately 2.5 µm provides an effective trapping layer for photocarriers during THz generation. Hydrogen ion implantation under reasonable conditions (300 keV, 1 × 1015 cm−2) for fabrication of efficient GaAs PCAs is found to be reproducible.