Closely spaced and separately contacted two-dimensional electron and hole gases by in situ focused-ion implantation

Separately contacted layers of a two-dimensional (2D) electron gas and a 2D hole gas have been prepared in GaAs, which are separated by AlGaAs barriers down to 15 nm thickness. The molecular-beam-epitaxial growth was interrupted just before growth of the double-layer structure in order to use in situ focused-ion-beam implantation to pattern contacts which extend underneath the barrier. The two charge gases form upon biasing the p- and n-type contacts underneath and above the barrier in the forward direction and show independent transistor-like behavior.