Enhancement of THz emission from semiconductor surfaces

We have studied the generation of coherent pulses of terahertz (THz) radiation from semiconductor surfaces both experimentally and using a Monte-Carlo carrier dynamics simulation. Collimated THz beams are observed from surface-field THz emitters and three methods of improving the efficiency of these emitters are demonstrated: (i) by applying a magnetic field, (ii) by reducing the effective refractive index of the device and (iii) by altering the geometry of the device. An enhancement of 21/spl times/ is seen in a prism based GaAs/InAs THz emitter.