InAlAs/InGaAs heteroestructures for THz generation

We present a microscopic analysis of current fluctuations in InAIAs/InGaAs slot diodes (base of HEMT devices). An ensemble Monte Carlo simulation is used for the calculations. We analyze the origin of the strong THz oscillations appearing when the bias surpasses 0.5 V. This effect is apparently caused by the presence of Gunn-like oscillations whose dynamics is controlled by ballistic Gamma-valley electrons in the channel. These carriers are capable to reach extremely high velocities due to (i) the influence of degeneracy effects, which significantly reduces the rate of scattering mechanisms, and (ii) the presence of the recess, which strongly accelerate the electrons, launching them into the drain region. The influence of the effective distance travelled by the domain and the recess length are analyzed in order to improve the control of the frequency and magnitude of the oscillations.