Pulsed terahertz time domain spectroscopy of vertically structured photoconductive antennas

摘要

We present a terahertz u0001THzu0002 photoconductive emitter structure, which employs a n-doped layernunderneath a low-temperature-grown GaAs region to enable the THz transient to couple verticallynthrough a defined mesa. A nonlinear bias dependence is observed, yielding an order in magnitudenimprovement in power for a mesa device with a 100 u0001m2narea over a conventional planar controlnreference device at 32 V and 5 mW illumination power. We relate the bias dependence of the THznsignal to the breakdown voltage observed in the current-voltage characteristic. Reducing the antennangap size through reducing the thickness of the low temperature-GaAs region below 1 u0001m shows anlarge improvement in the bandwidth of the device, with an enhancement of the normalized intensitynbetween 0.2 to 2 THz for a bow-tie antenna geometry. © 2010 American Institute of Physics.