SUBSTRATE-EPITAXIAL LAYER INTERFACE EFFECTS ON ALGAAS GAAS HETEROSTRUCTURE DEVICE PROPERTIES

Device characteristics of AlGaAs/GaAs heterostructure field effect transistors fabricated by molecular-beam epitaxial growth are related to the condition of the substrate-epitaxial layer interface. The presence of carbon on the GaAs wafer surface prior to growth has been found to produce a p-type, conducting interfacial region. We demonstrate that the concentration of carbon on the wafer surface can be significantly reduced by exposing the wafers to ultraviolet radiation. Depletion- and enhancement-mode device transfer characteristics and transconductance curves have been obtained on heterostructure wafers that were subjected to an ultraviolet-ozone surface preparation. A comparison of these results with the device properties of wafers receiving a standard cleaning procedure is presented. A model describing the interaction between the interfacial p-type region and the two-dimensional electron gas channel is also included.