Hole trapping time measurement in low-temperature-grown gallium arsenide

Abstract

We study hole dynamics in GaAs layers grown by molecular-beam epitaxy at 270 °C by two-color pump-and-probe experiments employing femtosecond 800-nm-wavelength pulses for sample’s excitation and 9-μm-wavelength pulses for probing the induced intervalence band absorption. Hole trapping time in as-grown, undoped layer is equal to 2 ps; it increases after thermal annealing or Be doping, and decreases in Si-doped layer. The mechanism of the hole trapping is discussed; it is shown that experimental observations are consistent with the hole trapping at neutral arsenic antisites model.

Semiconductor materials for ultrafast optoelectronic applications

“…7), these transitions being approximately by one order of magnitude more intense than the free-electron absorption. It has been found in [19] that the hole trapping time in as-grown LTG GaAs is of the order of 1 ps and more that 10 times longer in the annealed material. The correlation of the values of this parameter with the changes of As Ga defect state induced by additional doping of the layers has led to the conclusion that photoexcited holes in LTG GaAs are mainly trapped by neutral As antisites.…”

“…Direct monitoring of the photoexcited hole density dynamics in the valence band of LTG GaAs was performed by using two-colour pump-and-probe technique [19]. Nonequilibrium carriers were excited by femtosecond nearinfrared (800 nm) pulses and probed with 9 µm wavelength mid-infrared pulses.…”

Semiconductors for terahertz photonics applications

“…Sample annealing slows done the dynamics by approximately 10 times. Because all this experimentally observed variation of the hole trapping times correlates with the changes of the neutral As-antisite density in the LTG GaAs, it has been concluded in [79] that these defects are the main hole traps in this material.…”

“…Also, the dynamics of the electron trap population can be monitored by the nearinfrared probe pulses generated by an optical parametric oscillator [78]. Direct measurement of the hole density dynamics in the valence band of LTG GaAs was performed in [79] by an original twocolour pump-and-probe-technique. In this experiment, the non-equilibrium electrons and holes were excited by femtosecond optical pulses at the wavelength of 800 nm and the inter-valence band transitions were probed with 9-µm wavelength mid-infrared (MIR) pulses.…”

Low-Temperature MBE Grown GaAs for Pulsed THz Radiation Applications

“…The reduction of the THz power transmitted through the sample under investigation due to its absorption by optically excited electrons was easily measurable even at their densities as low as 10 16 cm −3 . For the hole trapping time measurement, a novel optical probe -mid--infrared (MIR) (the wavelength of 9 µm) probe technique [2] was used. The latter wavelength corresponds to the resonance transitions between the heavy and light hole valence bands, therefore, the light absorption by the free holes at the probe wavelength is at least 20 times larger than the free-electron absorption.…”