Carrier dynamics of indium arsenide quantum dash photoconductive antennas under 1.55 μm photo-excitation
Abstract
Indium arsenide (InAs) quantum dashes (QDash) grown on semi-insulating indium phosphide (SI-InP) wafers were fabricated into photoconductive antennas (PCAs) to investigate the effect of a varying number of QDash monolayers (ML) on the carrier dynamics. The samples were characterized using terahertz- time-domain spectroscopy (THz-TDS) with 1.55 μm excitation to isolate the THz emission of the QDashes from the bulk. A 90% THz intensity enhancement was observed from the sample with 7 MLs (QDash2) compared to the sample with 5 MLs (QDash1). This was attributed to its increased number of photocarriers and enhanced quantum confinement. Additionally, the QDash2 sample exhibited a wider bandwidth in the THz frequency spectra, presumably due to its short carrier lifetime and high velocity. Power dependence measurements further revealed that QDash2 has better optical-to-THz conversion efficiency and higher saturation power than QDash1 based on its steeper slope and fitted saturation value, respectively.