Side gating in silicon germanium hetero-dimensional field effect transistors

Abstract

Investigation into the side gate control of a two-dimensional hole gas in a silicon germanium hetero-dimensional field effect transistor (HDFET) is presented. Side gates within these devices form pn junctions between a three-dimensional contact and a two-dimensional electron or hole (Fermi) gas. A procedure for a priori incorporation of offsets within the band profiles of strained silicon/silicon germanium heterostructures is presented. The desired band profiles are generated within a device simulator and results are compared to electrical measurements on a silicon germanium p-type heterostructure field effect transistor to verify materials models and substrate design. The validated materials parameters and substrate design then serve as a basis for simulations of the HDFET structure. Spreading of the depletion regions between the side gates and the quantum well within the HDFET is studied. The electron or hole gas can be squeezed to the point where the quantum well region is fully depleted of charge carriers. Using this technique, a two-dimensional Fermi gas can be confined into a one-dimensional region forming a quantum wire. Manipulation of the quantum wire by side gate action is demonstrated. Our simulations of HDFET devices in silicon germanium verify that these devices can be achieved in silicon germanium materials and as a consequence, HDFET fabrication is compatible with complementary metal-oxide–silicon process technologies.