Search for: All records

Abstract Tellurium‐hyperdoped silicon (Si:Te) shows significant promise as an intermediate band material candidate for highly efficient solar cells and photodetectors. Time‐resolved THz spectroscopy (TRTS) is used to study the excited carrier dynamics of Si hyperdoped with 0.5, 1, and 2%. The two photoexcitation wavelengths enable us to understand the temperature‐dependent carrier transport in the hyperdoped region in comparison with the Si region. Temperature significantly influences the magnitude of transient conductivity and decay time when photoexcited by light with a wavelength of 400 nm. Due to the differential mobilities in the Si and hyperdoped regions, such dependence is absent under 266‐nm excitation. Consistent with the literature, the charge‐carrier lifetime decreases with increasing dopant concentration. It is found that the photoconductivity becomes less temperature‐dependent as the dopant concentration increases. In the literature, the photodetection range of Si:Te extends to a wavelength of 5.0 µm at a temperature of 20 K. The simulation shows that carrier diffusion, driven by concentration gradients, is strongly temperature dependent and impacts transient photoconductivity decay curves. The simulation also revealed that, in the hyperdoped regions, the carrier recombination rate remains independent of temperature. 

Abstract The ultrafast dynamics of photoexcited charge carriers are studied in micron‐scale crystals composed of the inorganic perovskite CsPbBr₃with time‐resolved terahertz spectroscopy. Exciting with photon energy close to the band edge, it is found that a fast (<10 ps) decay emerges in the terahertz photoconductivity with increasing pump fluence and decreasing temperature, dominating the dynamics at 4 K. The fluence‐dependent dynamics can be globally fit by a nonlinear recombination model, which reveals that the influence of different nonlinear recombination mechanisms in the studied pump fluence range depends on temperature. Whereas the Auger scattering rate decreases with decreasing temperature from 77 to 4 K, the radiative recombination rate increases by three orders of magnitude. Spectroscopically, the terahertz photoconductivity resembles a Drude response at all delays, yet an additional Lorentz component due to an above‐bandwidth resonance is needed to fully reproduce the data.