Carrier dynamics and surface vibration-assisted Auger recombination in porous silicon

Ammar Zakar, Rihan Wu, Dimitri Chekulaev, Vera Zerova, Wei He, Leigh Canham, Andre Kaplan

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Excitation and recombination dynamics of the photoexcited charge carriers in porous silicon membranes were studied using a femtosecond pump-probe technique. Near-infrared pulses (800 nm, 60 fs) were used for the pump while, for the probe, we employed different wavelengths in the range between 3.4 and 5 μm covering the mediumwavelength infrared range. The data acquired in these experiments consist of simultaneous measurements of the transmittance and reflectance as a function of the delay time between the pump and probe for different pump fluences and probe wavelengths. To evaluate the results, we developed an optical model based on the two-dimensionalMaxwell-Garnett formula, incorporating the free-carrier Drude contribution and nonuniformity
of the excitation by the Wentzel-Kramers-Brillouin model. This model allowed the retrieval of information about the carrier density as a function of the pump fluence, time, and wavelength. The carrier density data were analyzed to reveal that the recombination dynamics is governed by Shockley-Read-Hall and Auger processes, whereas the diffusion has an insignificant contribution. We show that, in porous silicon samples, the Auger recombination process is greatly enhanced at the wavelength corresponding to the infrared-active vibrational modes of the molecular impurities on the surface of the pores. This observation of surface-vibration-assisted Auger recombination is not only for porous silicon in particular, but for low-dimension and bulk semiconductors in general. We estimate the time constants of Shockley-Read-Hall and Auger processes, and demonstrate their wavelength dependence for the excited carrier density in the range of 1018–1019 1/cm3.We demonstrate that both processes are enhanced by up to three orders of magnitude with respect to the bulk counterpart. In addition, we provide a plethora of the physical parameters evaluated from the experimental data, such as the dielectric function and its dependence on the injection level of the free carriers, charge-carrier scattering time related high-frequency conductivity, and the free-carrier absorption at the midwave infrared range.
Original languageEnglish
Article number155203
JournalPhysical Review B
Publication statusPublished - 10 Apr 2018


Dive into the research topics of 'Carrier dynamics and surface vibration-assisted Auger recombination in porous silicon'. Together they form a unique fingerprint.

Cite this