Field impoverishment modes in a diode with an AlxGa1-xAs/GaAs heterojunction: a simulation analysis

The authors have examined previously the possibility of the formation of low-field domains as opposed to the traditional high-field domains found in Gunn diodes. Initial electron distributions that may lead to the growth of these domains are now further examined by numerical simulation with the purpose of finding conditions that are easier to meet in practice. It is confirmed that a significant number of electrons in the upper valleys is a necessary condition. However, it is found that the charge neutrality, uniform distribution in physical space, and direction of the wave number that were imposed in the previous simulation are not determinant. A Al_xGa_1-xAs(n)/GaAs(n) abrupt heterojunction is studied next in the frame of the Boltzmann transport equation. It is predicted that it may be used as an electron launcher into upper valleys for impoverishment field domains, provided the composition makes the ternary compound an indirect band gap semiconductor. When the injection guarantees 50% of the electrons in the satellite valleys at the heterojunction plane, the authors´ results show that, at a distance of 0.25 μm from the heterojunction interface, as much as 30% of the total number of electrons remains in the upper valleys. A diode that exhibits the formation of repetitive transit time field impoverishment modes is proposed