Temperature-Dependent Dynamics of Charge Carriers in Tellurium Hyperdoped Silicon

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.