Spectral dependencies of terahertz emission from InAs and InSb

Abstract

Spectral dependences of the THz radiation from the laser-illuminated surfaces of InAs and InSb have been investigated experimentally at high optical fluences for the laser wavelengths ranging from 0.6 to 2μm. Efficient THz generation was discovered in the excitation range around 1.6μm. The influence of the intervalley scattering was clearly evidenced. The energy position of the subsidiary conduction band valleys was evaluated from this study to be equal 1.08 and 0.53 eV for InAs and InSb, respectively. It has been concluded that THz emission at high excitation fluencies is dominated by the shift current effect.

Excitation wavelength dependence of terahertz emission from InN and InAs

“…Recently, Adomavicius et al 12 have measured the spectral dependence of terahertz emission from ͑111͒ InAs at high carrier densities, where nonlinear effects are the dominant terahertz generation mechanism. Such high optical fluences, however, are not suitable for compact fiber lasers.…”

Semiconductor materials for ultrafast optoelectronic applications

“…On the other hand, dependences of the THz radiation efficiency from femtosecond laser illuminated InAs surfaces on photon energy measured in [53] are leading to an opposite conclusion. The results of such measurements are presented in Fig.…”

“…This evidences that small band gap and large excess energy of photoexcited electrons are not the most important factors determining efficient THz pulse generation. On the opposite, electrons with large excess energies will be additionally scattered to the subsidiary valleys as in InSb [53] or their effective mass will significantly increase (CdHgTe [55]), thus the electron separation from the holes will be less efficient and the Dember photovoltage induced by this separation will be relatively small.…”

“…Investigations of THz radiation from femtosecond laser excited semiconductor surfaces were already used for determining the intervalley energy separation in the conduction bands of various compounds [53], the electron inter-valley scattering rate in Ge [60], and the electron energy relaxation rate in CdHgTe [61].…”

Polarization imaging of imperfect m-plane GaN surfaces

“…In the case of semiconductors with a narrow band gap and high carrier mobility, such as InAs, the photo-Dember effect is the dominant THz radiation mechanism. 13 In contrast, THz radiation from the surface of relatively wide band gap semiconductors such as GaAs is known to be due to the current surge effect, that is, the phenomenon in which a drift current is induced by band bending near the surface. 14 Therefore, we conclude that the J ⊥ on the surface of GaN is induced by the current surge effect.…”