Diffusion and drift in terahertz emission at GaAs surfaces

Abstract

We study terahertz (THz) emission from GaAs as a function of photon energy and electric field. THz radiation arises from transport of photogenerated charge in an electric field and by hot carrier diffusion (the photo-Dember effect). These mechanisms can be separated by experiments in which either the electric field or the kinetic energy of the carriers is varied. For electric fields E∼4 kV/cm, we find that the electric field controls THz emission for carrier temperatures kBTC⩽0.1 eV, while hot-carrier diffusion dominates for kBTC≈1 eV. Both mechanisms contribute at intermediate fields and carrier temperatures. Our results are consistent with estimates of the relative magnitudes of these two effects.

Terahertz Electromagnetic Waves from Semiconductor Epitaxial Layer Structures: Small Energy Phenomena with a Large Amount of Information

“…We also note that the other generation mechanism of the surge current exists: the photo-Dember effect induced by the carrier diffusion dominating in narrow gap semiconductors such as InAs. In GaAs, the drift motion is dominant because, even in the presence of the negligibly low electric field (several kV/cm), the photo-Dember effect is quite small owing to the slight excess energy Heyman et al, 2003). The photo-Dember effect is out of the scope of the present chapter.…”

Oscillations of electron–hole plasma in terahertz emitters

“…At low generation density n exc << n eq , Eq. (6) reduces to (12) In this limit, the frequency of plasma oscillations becomes position-independent, and it is controlled by the density n eq of the uniformly distributed equilibrium electrons.…”

“…The rapid progress in THz technology over the past two decades [8][9][10] offered an opportunity for a direct observation of the optically generated electron-hole plasma oscillations from the time-resolved measurements of THz emission. However, the temporal waveforms of THz radiation observed in most experimental studies evidence the onset of a single current surge and do not indicate the development of plasma oscillations [11][12][13][14]. Several attempts have been made to detect the oscillations of electron-hole plasma generated by the femtosecond optical pulse.…”

Temperature dependence of terahertz emission from InMnAs

“…Many studies have examined terahertz emission from a variety of III-V semiconductors surface, including InAs, InSb, InP, and GaAs. [5][6][7][8][9][10][11] In particular, magnetic-field-induced enhancement of terahertz radiation from nonmagnetic semiconductor surfaces has been investigated thoroughly. [11][12][13][14][15][16] Recently, terahertz emission from ferromagnetic metal films 17,18 and from the dilute ferromagnetic semiconductor GaMnAs ͑Ref.…”