Monte Carlo Study On Electrons Transport Of Terahertz GaAs/AlGaAs Quantum-well Detectors

In this work, we have investigated the detailed behavior of electrons transporting in terahertz (THz) GaAs/Al_0.03Ga_0.97As quantum well photo-detectors at low temperature and low electric field by establishing a Monte Carlo simulation model running in Visual Fortran software. In the established model, many kinds of electrons scattering mechanisms are involved while considering the non-parabolic band model. We mainly studied the transporting behavior of excitated electrons including: the concentration distribution of excitated electrons at different times and in different valley, the drift velocity and electron mobility characteristic of those electrons and the current response of THz photo-detectors. Based on the simulated results, we also discussed the macroscopic characteristics of the THz photo-detectors. The results are very useful to the current study of THz detectors. The paper mainly contains the following works:1. By simulating the concentration distribution of the excitated electrons transporting in THz GaAs/Al_0.03Ga_0.97As quantum well photo-detectors at different times and in different valley, we observed that almost all excited electrons are transporting inΓvalley. Based on this, we analyzed the drift velocity and mobility characteristics of excitated electrons. On the other hand, a special phenomenon is observed, which is the drift velocity is increased with the increasing of temperature, which is different from the result in former work. Focusing on this, we discussed the possible causation and gave a proper explanation.2. By simulating the transient photo-current response of THz GaAsZAl_0.03Ga_0.97As quantum well photo-detectors, we didn't find obvious velocity over-shoot effect which often exists in infrared photo-detectors. Aiming at this phenomenon, we gave a proper explanation by theoretical analysis. After this, we further simulated the steady-state current and its dependences on the bias voltage.3. In viewing of the simulation results got by using the established model, we discussed the macroscopic characteristics of THz photo-detectors, including: a higher photo-conductive gain, a higher detecting sensitivity, and a lower noise level and made a detailed analyses on the dark current, which is the main cause of dark current noise. Beyond this, we represented the personal idea about the main disadvantage in current THz photo-detector and its future development.