Abstract
Electronic properties of InSb and InAs are sensitive to electric field due to their narrow forbidden energy gaps and big difference in effective masses of electrons in different conduction band valleys. Here we report impact ionization processes and redistribution of electrons between the Γ, L and X valleys induced by a single ultrashort terahertz (THz) pulse at 80 K temperature. Monte Carlo simulation revealed that electron motion in this case has near ballistic character. The threshold electric field of impact ionization increases as the THz pulse gets shorter, and the process of impact ionization essentially raises cooling rate of hot electrons. The L valley gets mainly occupied by electrons in InSb while the X valley holds the majority of electrons in InAs at strong electric fields, respectively above 20 kV/cm and 90 kV/cm. The calculated results are in good agreement with the available experimental data.
Highlights
Electronic properties of InSb and InAs are sensitive to electric field due to their narrow forbidden energy gaps and big difference in effective masses of electrons in different conduction band valleys
The observed nonlinear absorption and self-phase modulation of THz pulses were explained by ultrafast impact ionization processes driven by strong electric field
In this paper we present the results of Monte Carlo simulation in case when intense ultrashort, subpicosecondlong, THz pulse interacts with narrow-gap InSb and InAs semiconductors at T = 80 K
Summary
Electronic properties of InSb and InAs are sensitive to electric field due to their narrow forbidden energy gaps and big difference in effective masses of electrons in different conduction band valleys. When a semiconductor is illuminated with intense THz radiation, the average electron energy increases and the impact ionization process may begin[22]. The intervalley scattering of electrons and impact ionization in InAs were investigated at room temperature under the excitation of intense single-cycle THz 150 fs-long p ulses[14,17]. It was shown that at low temperature, T = 6 K, the threshold electric field of impact ionization in InAs was of the order of 10 kV/cm when nanosecond-long THz pulses were u sed[28]. In this paper we present the results of Monte Carlo simulation in case when intense ultrashort, subpicosecondlong, THz pulse interacts with narrow-gap InSb and InAs semiconductors at T = 80 K. We study impact ionization processes and corresponding hot electron dynamics, population of electrons in the Γ and higher L and X valleys and sequence of their transfer between the valleys under the action of ultrashort THz pulse
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