Evidence for the co-existence of two- and three-dimensional electron gases in the emitter of double barrier devices

Abstract

We have analysed the dimensionality of the emitter electron gas of double barrier devices (DBD) under bias and found evidence for the coexistence of both two- and three-dimensional (2D and 3D) electron gases. Magnetotunneling measurements performed on a series of n-type GaAs/(AlGa)As DBD with varying emitter doping profiles have shown that the electron gas may have a 2D and/or 3D character depending on the emitter doping level and on the applied bias. In devices with heavily doped emitter layers, electrons tunnel from 3D-states, whereas for lightly doped emitters a 2D-electron gas is formed in the emitter contact. For intermediary doping levels both 2D- and 3D-electron gases may coexist, depending on the applied bias.