Two dimensional electron transports for terahertz emission fromIn0.53Ga0.47As/In0.52Al0.48Asmultilayer structures illuminated by 1.55 μm-laser

Two dimensional electron gas (2DEG) transports in In_0.53Ga_0.47As/In_0.52Al_0.48As multilayer structure (MLS) illuminated by an ultrashort optical pulse with the central wavelength at 1.55 μm is investigated by ensemble Monte Carlo simulations. Terahertz (THz) pulses are calculated according to the transient photocurrent in the InGaAs layers. It is found that InGaAs/InAlAs MLS with narrower InGaAs layers has an advantage in generating large temporal change in the transient photocurrent, which thereby is able to increase the intensity of THz emission. Beryllium (Be)-doping in InGaAs layers provides a scattering channel to speed the decay of photocurrent, and is shown to be a factor in shaping the bipolar structure of THz temporal waveforms. Bandwidth of the generated THz emission is found to be mainly controlled by the laser pulse duration at low doping level, but at high doping level, the bandwidth is determined together by laser pulse duration and doping density.