Single-gated mobility modulation transistor

We have investigated an n-type field effect transistor based on a GaAs/AlGa As structure with a channel which consists of two tunnel-coupled quantum we lls. Modulation of channel conductivity is achieved through a change in ele ctron mobility under the effect of anticrossing of quantization levels in w ells while the concentration of carriers remains practically constant. With proper choice of the structural layout and doping profile, the transistor can be effectively controlled by the front gate only. The possibility of ob taining the highest amplitude of conductivity modulation by electron mobili ty suppression in one of the quantum wells and by varying tunnel coupling b etween the wells is investigated by numerical simulations. It is shown that . with a gradual decrease of electron mobility in one of the quantum wells, the conductivity modulation amplitude first increases, comes to a maximum, and then decreases due to suppression of tunnel coupling between wells by scattering of longitudinal momentum. The drain current dependence on the ga te voltage of the device under investigation shows two maxima; this feature allows the same device to be used as both an n- and p-type transistor.