Magnetophonon Resonance of Hot Electrons in n-InSb at 77 K

Magnetophonon resonances, which were first predicted by Gurevich and Firsov, have been observed in the hot electron mobility in pure n -InSb. The resonance experiment was carried out at 77 K in transverse magnetic field up to 22 kG with application of sufficiently small electric field to produce a slight change in the electron mobility. The quantity β in the formula µ=µ 0 (1-β E 2 ) was measured with extremely good accuracy ( Δ µ/µ 0 ∼10 -7 ) by adopting a bridge circuit. The minima in the quantity |β| were observed at magnetic fields, B =17.5, 11.3, 8.53, 6.89, 5.72, 4.83, 4.12, 3.68, 3.72, and 2.93 kG. These resonance extrema are attributed to resonant cooling of hot electrons due to optical phonon induced transitions from the high energy tail of the electron distribution near k z =0 at higher Landau levels to lower Landau levels. The extremal positions are well explained by taking the non-parabolicity of the conduction band of InSb into account.