Stimulated IR emission by quantum magnetoelectric photoeffect of narrow-gap semiconductors

A new type of lasing action of bulk semiconductors which are tunable in the quantum limit has been demonstrated in n-InSb. The population inversion has been achieved by passing a DC current J through the sample subjected to a transverse high magnetic field H up to 22T. At the quantum limit, the critical current density J(c) for lasing becomes as low as e.g. similar to 17 A/cm(2) for H = 10T at 43K, owing to the extremely high value of the gain, which originates from the singularity of the one-dimension-like density of states caused by the application of high magnetic fields. It has been pointed out that a small number of electrons populated occasionally in high energy states can trigger impact ionisation to cause the population inversion, acquiring the kinetic energy Delta epsilon, which is larger than the optical-phonon energy (h) over bar omega(op), from electromagnetic fields. The excitation process is closely related to the reduction in the bandgap energy, similar to-Delta epsilon, observed in crossed electric and magnetic fields at the quantum limit. Emission spectroscopy has effectively been applied to determine the band parameters at room temperature as well as at low temperatures.