Far-Infrared Recombination Radiation from Impact-Ionized Shallow Donors in GaAs

Radiation corresponding to transitions from excited shallow donor states and from conduction-band states to the donor ground state has been observed in impact-ionized GaAs at temperatures near 4.2^∘{}K. Spectral measurements show a main peak at a wavelength of 282 {μ} (4.4 meV), corresponding to a 2p→1s transition, and a broader continuum extending to higher photon energies. A total radiated power of 10^-7 W has been measured corresponding to an external quantum efficiency of about 10^-6.