Coherent Microwave Radiation from BiSb Alloys

Microwave radiation is observed from electrically biased semiconducting BiSb alloys. The radiation emitted from ${\mathrm{Bi}}_{92}$ ${\mathrm{Sb}}_8$ and its harmonics to the fourth order are very narrow band and coherent. The mechanism of emission is postulated to be a super-radiant maser effect due to transitions between paramagneticlike levels pumped by the electric current.