In this paper, we report on electrically pumped terahertz emitters based on silicon doped with boron acceptors. At cryogenic temperatures, three narrow spectral emission lines attributed to radiative transitions from p-like excited hydrogenic states to the s-like Γ8 ground state associated with the boron dopants were observed centered around 8 THz. The spectral emission line center frequencies were in remarkable agreement with values reported from absorption measurements and theoretical calculations. The total time-resolved terahertz emission power was found to be up to 31 μW per device facet. We have solved the rate equations describing the populations in the hydrogenic dopant states involved in the emission mechanism and derived expressions for the current pumping and temperature dependence of the emitted terahertz power, yielding excellent agreement with the experimental data. These results suggest that silicon-based terahertz emitters may be fabricated without epitaxial quantum wells. The observed temperature dependence suggests that electric field assisted thermal escape of carriers from upper hydrogenic states may be responsible for lower output powers at higher temperatures.
Terahertz emission from lithium doped silicon under continuous wave interband optical excitation