INTERBAND IMPACT IONIZATION BY TERAHERTZ ILLUMINATION OF INAS HETEROSTRUCTURES

Experimental studies of InAs heterostructures illuminated by far-infra red (FIR) radiation reveal an abrupt increase in the charge density fo r FIR intensities above a threshold value that rises with increasing f requency. We attribute this charge density rise to interband impact io nization in a regime in which omega tau(m) similar to 1, where tau(m) is the momentum relaxation time, and f=omega/2 pi is the FIR frequency . The dependence of the density rise on the FIR field strength support s this interpretation, and gives threshold fields of 3.7-8.9 kV/cm for the frequency range 0.3-0.66 THz. (C) 1996 American Institute of Phys ics.