Abstract

The development of high-speed devices has recently stimulated the application of low-temperature-grown GaAs (LTG) epilayers because of their subpicosecond carrier lifetime and the high dark-resistance. Here, we report on fabrication and THz-emission characterization of photoconductive dipole antennas made from low-temperature-grown GaAs on sapphire. The LTG epilayers are lifted-off the GaAs substrate, transfered to a sapphire substrate and bonded by Van-der-Waals bonding. Sapphire provides good transparency for optical wavelengths combined with a high transmission in the THz-regime and avoids leakage currents through the substrate. The preparation of the LT-GaAs/sapphirc antennas followes the procedure, which was first presented by Yablonovitch et al..' The antenna is dc biased and excited from the sapphire side by 150-fs pulses from a Ti:sapphirc laser with a photon energy of 1.614 eV and a repetition rate of 76 MHz.

© 1996 IEEE