Fluence and polarisation dependence of GaAs based Lateral Photo-Dember terahertz emitters

Abstract

We characterise THz output of lateral photo-Dember (LPD) emitters based on semi-insulating (SI), unannealed and annealed low temperature grown (LTG) GaAs. Saturation of THz pulse power with optical fluence is observed, with unannealed LTG GaAs showing highest saturation fluence at 1.1 ± 0.1 mJ cm −2 . SI-GaAs LPD emitters show a flip in signal polarity with optical fluence that is attributed to THz emission from the metal-semiconductor contact. Variation in optical polarisation affects THz pulse power that is attributed to a local optical excitation near the metal contact.

Multiple double-metal bias-free terahertz emitters

“…The results show that the most powerful emitters are Au/Pb fabricated directly of SI-GaAs, the Au/Pb insulated emitters as mentioned above, is weaker working only on the difference of quenching efficiency of Au and Pb stripes. Double-metal emitters demonstrate a dependence on the optical pump polarisation similar to the one encountered in 3,18 , all the measurements presented here are made with a polarisation perpendicular to the metal edges. Multiple double-metal emitters have similar signal to noise performance compared with large gap SI-GaAs photoconductive antennas measured in a terahertz time-domain spectroscopy (THz-TDS) experiment.…”

“…Band bending near the surface of a semiconductor can cause terahertz emission 8 and has been shown to influence LPD emitters in 3 and to modify the polarity of terahertz pulses under intense optical fluence 3,9 . Therefore, in the repeatable structures that we show here we used metal pairs that would also create terahertz emission due to different Schottky barrier potentials.…”

“…The cause of saturation within the directly bonded double-metal emitters is likely to be due to the charge accumulation within the depletion region. The drift current of the electrons from the metal to the semiconductor is reduced for higher fluences, at high carrier concentrations the barrier height decreases due to the higher carrier density and higher Fermi energy in the semiconductor 3,9 . The time domain scans and the corresponding power spectrum for the Au/Pb insulated with SiO 2 and Au/Pb uninsulated are shown in Fig.…”

Large area InN terahertz emitters based on the lateral photo-Dember effect

“…Polarization dependent diffraction of the excitation laser on the metal edges, affecting the light intensities, and therefore, the distribution of the excited charge carriers under the metal, may also play an important role. 18 In any case, the effect of the microstructure on the terahertz emission needs to be further explored since our study clearly demonstrates the significant potential for structural optimization of this type of emitters.…”

Effects of a thin nitrogen-doped layer on terahertz dynamics in GaAs containing InAs quantum dots

“…When the dynamics around the semiconductor surface is focused, the observation of the terahertz (THz) wave emitted from the surface can be considered to be a good tool. For instance, the direction of the surface depletion can be identified as the initial phase of the THz wave [22][23][24][25]. Recently, we reported the phase inversion of a THz wave emitted from a GaAs crystal that included InAs QDs, which was attributed to the lattice-mismatched strain [26].…”