Ultrafast carrier dynamics inBr+-bombarded InP studied by time-resolved terahertz spectroscopy (original) (raw)
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Ultrafast carrier response of Br+-irradiated In0.53Ga0.47As excited at telecommunication wavelengths
Journal of Applied Physics, 2012
We present results of infrared pump—terahertz probe experiments applied to a set of In0.53Ga0.47As films irradiated with heavy ions (Br+) at doses from 109 to 1012 cm−2. Photoexcitation at 1400 nm (0.89 eV) allowed us to characterize the response close to telecommunications’ wavelengths whilst avoiding the intervalley carrier scattering observed when a shorter wavelength excitation is used. The excitation fluence was varied in our experiments in order to characterize the dynamics in detail: the lifetimes and mobilities of both electrons and holes were retrieved, and the trap filling and carrier diffusion were clearly observed. The In0.53Ga0.47As film irradiated by the dose of 1012 cm−2 exhibits simultaneously ultrashort electron lifetime (∼300 fs) and very high electron mobility (2800 cm2V−1s−1). These findings are particularly important for the design of terahertz emitters controlled by lasers operating at standard telecommunication wavelengths.
Ultrafast Electron Dynamics in GaAs and InP Studied by Time-Resolved Terahertz Emission Spectroscopy
Japanese Journal of Applied Physics, 2004
We studied the ultrafast dynamics of electrons generated by tunable femtosecond optical pulses having positive and negative excess energies in GaAs and InP by observing the temporal waveform of THz radiation emitted from biased photoconductive antennas. Sub-picosecond intraband relaxation was observed when the excess energy was positive. When excited by optical pulses having negative excess energies, it was observed that the THz waveform had a picosecond decay, which was attributed to the transition from the Urbach state to the free carrier state of electrons on the picosecond time scale. This dynamical behavior was found to be very sensitive to the applied electric field in the range of several kV/cm. The largest THz signal was obtained by pumping the emitter at the band-gap energy.
Ultrafast trapping times in ion implanted InP
Journal of Applied Physics, 2002
As ϩ and P ϩ implantation was performed on semi-insulating ͑SI͒ and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1ϫ10 16 cm Ϫ2 and p-type InP was implanted with doses between 1 ϫ10 12 and 1ϫ10 16 cm Ϫ2. Subsequently, rapid thermal annealing at temperatures between 400 and 700°C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implanted p-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity.
Picosecond InP photoconductors produced by deep implantation of heavy ions
1996
Generation and detection of high power short optical pulses are of interest for applications such as high speed switching and optically controlled microwave generation. Such systems based entirely on semiconductor technology are highly desirable. In our experiments significant enhancement in the response of metal-semiconductor-metal photoconductive switches fabricated on Fe doped semi-insulating InP with heavy ion N(superscript +3) implantation has been
Picosecond InP photoconductors produced by deep implantation of heavy ions
Infrared Detectors for Remote Sensing: Physics, Materials, and Devices, 1996
Generation and detection of high power short optical pulses are of interest for applications such as high speed switching and optically controlled microwave generation. Such systems based entirely on semiconductor technology are highly desirable. In our experiments significant enhancement in the response of metal-semiconductor-metal photoconductive switches fabricated on Fe doped semi-insulating InP with heavy ion N +3 implantation has been observed. The response tail of the devices was effectively eliminated, resulting in FWHM pulse widths reduction from 200 ps (when unimplanted) to less than 40 ps for 4.5 m gap device. No appreciable decrease in the breakdown field was observed. The dependence of spectral sensitivity on implantation dose was also studied. By proper optimization of the detector circuit, and use of high power semiconductor lasers with saturable absorber, generation of microwave signals in excess of 25 GHz and several volts could be achieved.
Hot electron cooling in InSb probed by ultrafast time-resolved terahertz cyclotron resonance
Physical Review B, 2021
Measuring terahertz (THz) conductivity on an ultrafast timescale is an excellent way to observe charge-carrier dynamics in semiconductors as a function of time after photoexcitation. However, a conductivity measurement alone cannot separate the effects of charge-carrier recombination from effective mass changes as charges cool and experience different regions of the electronic band structure. Here we present a form of time-resolved magneto-THz spectroscopy that allows us to measure cyclotron effective mass on a picosecond timescale. We demonstrate this technique by observing electron cooling in the technologically significant narrow-bandgap semiconductor indium antimonide. A significant reduction of electron effective mass from 0.032 to 0.017 m e is observed in the first 200 ps after injecting hot electrons. The measured electron effective mass in InSb as a function of photoinjected electron density agrees well with conduction band nonparabolicity predictions from ab initio calculations of the quasiparticle band structure.
Applications of time-resolved terahertz spectroscopy in ultrafast carrier dynamics (Invited Paper)
Chinese Optics Letters, 2011
Three time-resolved terahertz (THz) spectroscopy methods (optical-pump/THz-probe spectroscopy, THzpump/THz-probe spectroscopy, and THz-pump/optical-probe spectroscopy) are reviewed. These are used to characterize ultrafast dynamics in photo-or THz-excited semiconductors, superconductors, nanomaterials, and other materials. In particular, the optical-pump/THz-probe spectroscopy is utilized to investigate carrier dynamics and the related intervalley scattering phenomena in semiconductors. The recent development of intense pulsed THz sources is expected to affect the research in nonlinear THz responses of various materials.
Journal of Applied Physics, 2010
We present a model reproducing the instrumental response of a time-domain spectrometer that integrates photoconductive transmitter and receiver antennas made on identical proton-bombarded GaAs substrates. This model is used to determine the ultrafast capture time of the photoexcited carriers by the ion-bombardment-induced traps. A 0.5 ps capture time can be extracted for a low laser pump fluence of 0.66 J / cm 2 per pulse. This carrier trapping time gets longer as the pump fluence increases. This behavior is explained by a gradual filling of the traps that are distributed over a 1 m depth from the GaAs surface. This interpretation is supported by time-resolved measurements obtained on the same photoconductive material using both an 820 nm pump/ terahertz-probe transmission experiment and a degenerate 760 nm pump/probe reflectivity experiment. The differential transmission and reflectivity dynamics are reproduced using a biexponential function which correctly describes the photoexcited carrier relaxation and transport dynamics in this material. The strong agreement observed between these different measurements reinforces the validity of the theoretical model used to reproduce the instrumental response of the terahertz setup.