NEGATIVE MASS CYCLOTRON-RESONANCE MASER

Physical principles, design and operation characteristics of a negative mass cyclotron resonance maser in p-type germanium are considered in this paper. The formation of anisotropic inverted distributions of negative effective mass heavy holes in strong electric and magnetic fields E parallel-to H parallel-to [001], resulting in negative conductivity in the millimetre and submillimetre wavelength ranges, is discussed. The generation is observed at lambda almost-equal-to 0.9 to 8 mm in low compensated germanium samples with the hole concentration range N0 almost-equal-to 2 x 10(12) to 2 x 10(14) cm-3 at low temperatures T less-than-or-equal-to 25 K in electric fields E almost-equal-to 40 to 350 V cm-1. The maser frequency is tuned by the magnetic field corresponding to a cyclotron resonance frequency of carriers with an effective mass of m(c) almost-equal-to 0.4 M(o). The spectral width of the emission in single mode operation does not exceed several megahertz. A pulse duration of tau almost-equal-to 1 to 200-mu s and a repetition rate of f(rep) almost-equal-to 1 to 200 Hz has been obtained limited by sample heating. Possibilities of improving the maser characteristics in p-Ge as well as in other A(III) B(v) semiconductors and the perspectives of new frequency tuning methods due to the application of uniaxial stress and magnetic field are demonstrated.