Far-Infrared Recombination Emission inn-Ge andp-InSb

Abstract

Far-infrared recombination emission with wavelengths longer than 90 μ was observed under pulsed conditions from the impact ionization of impurity in $n$-Ge(Sb) and $p$-InSb samples at 4.2°K. A fast-response $n$-InSb free-electron bolometer was used as the detector and various filters were used to isolate the spectral regions. Emission with $h\nu$ near 4 meV is interpreted as recombination of free carriers with the lowest excited state of the impurity for both $n$-Ge and $p$-InSb. For the $n$-Ge sample, emission with $h\nu \sim 7.8$ meV is attributed to electron transitions from an excited state to the ground state. There was also some indication of emission with photon energies larger than the ionization energy of 9.7 meV of Sb. For $p$-InSb, emission was observed at photon energies near the impurity ionization energy of about 7.5 meV. This is attributed to the recombination of free holes with the ground state of the impurity. Under certain conditions of pulse duration and electric field, an afterglow was observed after the electric field was removed from the samples. An explanation is suggested for this phenomenon.