Terahertz emission from GaAs and InAs in a magnetic field
نویسندگان
چکیده
We have studied terahertz ~THz! emission from InAs and GaAs in a magnetic field, and find that the emitted radiation is produced by coupled cyclotron-plasma charge oscillations. Ultrashort pulses of THz radiation were produced at semiconductor surfaces by photoexcitation with a femtosecond Ti-sapphire laser. We recorded the integrated THz power and the THz emission spectrum as a function of magnetic field at fields up to 5.5 T, and as function of temperature for T510– 280 K. The maximum observed THz power is ;1.6310 J/pulse ~12 mW average power! from n-InAs (1.8310 cm! at B53.2 T. We compare our results to semiclassical models of magnetoplasma oscillations of bulk free carriers and damped motion of free carriers in a twodimensional electron gas. The bulk model describes THz emission from n-GaAs at all magnetic fields, and InAs at B50. It fails to describe THz emission from InAs at nonzero magnetic fields. We show that a model including both bulk plasma oscillations and THz emission from a surface accumulation layer describes THz emission from InAs in a moderate magnetic field, but this model does not completely describe emission at fields uBu.1.0 T.
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