Terahertz emission from p-lnAs due to the instantaneous polarization

Abstract

Terahertz radiation from differently doped n- and p-type InAs crystal surfaces was investigated by time-resolved measurement. Large increase of the emitted terahertz power has been observed for p-InAs samples with the p-doping levels of approximately 1016–1017cm−3. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in this layer.

Strong terahertz emission from (100) p-type InAs

“…2 is possibly due to a minor contribution from bulk optical rectification, although it is not possible to completely rule out other nonlinear processes-such as electric-field-induced optical rectification or surface nonlinear optical response-without further experimental evidence. 12,18 The dependence of the THz power on the temperature has been measured over the range 20-300 K. The results are shown in Fig. 4, normalized to a power of 1 at 300 K. In contrast to undoped, residual n-type ͑100͒ InAs, for which a maximum in power is observed at ϳ170 K, 9 but in agreement with data for undoped ͑111͒ InSb, 10,11 our data show a steady decrease in power with temperature.…”

“…As expected from the equations governing the optical rectification, 17 the cos 2 dependence is consistent with optical rectification for ͑100͒ orientation, just as a cos 3 dependence has been noted for ͑111͒ orientation. 12 A cos 2 dependence has been observed previously for ͑100͒ orientation in, for example, n-type InAs ͑Ref. 18͒ and n-type InSb.…”

“…We have also measured at an azimuthal angle = 90°, and observed a similar behavior. In comparison to pump power/ fluence dependencies of THz signals given earlier, 12,18 our measurements are at much lower pump fluences ͑Ͻ1 J/cm 2 ͒ and are characteristic of a photocurrent surge mechanism, more specifically the photo-Dember effect as re- ported previously for THz generation under low excitation fluences. 17,19 As the radiating dipole due to the current surge is oriented perpendicular to the surface, the emitted THz radiation would be p polarized.…”

“…Adomavičius et al 12 have recently reported on the emission of THz radiation from p-InAs. They point out the critical importance of the polarity of the dopant, showing acceptor-doped InAs to be a far stronger emitter than donordoped InAs.…”

Semiconductors for terahertz photonics applications

“…New experimental facts emerged after discovery [150] that a p-type InAs is a better THz emitter than an n-type InAs. This fact was explained in [150] as a consequence of the EFIOR effect induced by the surface field in the p-InAs.…”