Terahertz emission from GaAs and InAs in a magnetic field - art. no. 085202

We have studied terahertz (THz) emission from InAs and GaAs in a magnetic f ield, and find that the emitted radiation is produced by coupled cyclotron- plasma charge oscillations. Ultrashort pulses or THz radiation were produce d at semiconductor surfaces by photoexcitation with a fermosecond Ti-sapphi re laser. We recorded the integrated THz power and the THz emission spectru m as a function of magnetic field at fields up to 5.5 T, and as function of temperature for T= 10-280 K. The maximum observed THz power is similar to 16 x 10(-13) J/pulse (12 muW average power) from n-InAs (1.8 x 10(16) cm(-3 )) at B=3.2 T. We compare our results to semiclassical models of magnetopla sma oscillations of bulk free carriers and damped motion of free carriers i n a two-dimensional electron gas. The bulk model describes THz emission fro m n-GaAs at all magnetic fields. and InAs at B=0. It fails to describe THz emission from InAs at nonzero magnetic fields. We show that a model includi ng both bulk plasma oscillations and THz emission from a surface accumulati on layer describes THz emission from InAs in a moderate magnetic field, but this model does not completely describe emission at fields \B \ > 1.0 T.