Transient velocity overshoot dynamics *in GaAs for electric fields
نویسندگان
چکیده
We have experimentally studied the transient velocity overshoot dynamics of photoexcited carriers in GaAs for electric fields as great as 200 kV/cm. Time domain waveforms proportional to the velocity and the acceleration of carriers have been acquired? respectively, from guided and free-space radiating signals which contain terahertz frequency components. The measurements demonstrated that the degree of overshoot was maximized for an electric field on the GaAs between 40 and 50 kV/cm when 1.44-eV photons in an 80-fs laser pulse excited the sample. For carriers excited with higher initial energy ( 1.55 eV), the degree of overshoot decreased and the maximum degree of overshoot occurred at a higher electric field.
منابع مشابه
Nonlinear free-carrier velocity induced by intense Terahertz pulse in photoexcited semiconductor materials
The transient absorption bleaching and velocity overshoot of photoexcited carriers in GaAs and Si have been observed by the intense few-circle terahertz (THz) probe pulse in the optical pump-terahertz probe (OPTP) configuration. The free-carrier THz nonlinearity is attributed to the transient electron redistribution in conduction band induced by the strong THz electric field component.
متن کاملPossible Generation of Transient THz Electronic Drift Effects in a Semiconductor by a High Electric Field
Using the Boltzmann equation formalism for a simple semiconductor model, the transient drift velocity of the electrons is computed when a high uniform electric field is suddenly turned on. Rapid oscillations superimposed on an overshoot behaviour are obtained. It is showed that this behaviour results from the combined action of the field and of the electron-phonon
متن کاملTransient Natural Convection Flow on an Isothermal Vertical Wall at High Prandtl Numbers: Second-Order Approximation
The method of matched asymptotic expansions, which has been used in previous studies of steady natural convection flow, is extended here to transient natural convection flow at high Prandtl number (Pr). Second-order expansion solutions, valid for large Prandtl numbers, are presented for the transient natural convection flow near a vertical surface which undergoes a step change in temperature. T...
متن کاملEnhancing the photomixing efficiency of optoelectronic devices in the terahertz regime
A method to reduce the transit time of majority of carriers in photomixers and photo detectors to < 1 ps is proposed. Enhanced optical fields associated with surface plasmon polaritons, coupled with velocity overshoot phenomenon results in net decrease of transit time of carriers. As an example, model calculations demonstrating > 280× (or ∼2800 and 31.8 μW at 1 and 5 THz respectively) improveme...
متن کاملHigh-field transport in two-dimensional graphene
Transport of carriers in two-dimensional graphene at high electric fields is investigated by combining semianalytical and Monte Carlo methods. A semianalytical high-field transport model based on the high rate of optical phonon emission provides useful estimates of the saturation currents in graphene. For developing a more accurate picture, the nonequilibrium (hot) phonon effect and the role of...
متن کامل