METAL-InAs CONTACT FOR VERTICAL HETEROJUNCTION TRANSISTORS
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Unipolar transistors of the metal base type have long been of interest for high speed applications. Of particular interest recently are devices in which an epitaxial n++ semiconductor, such as InGaAs, replaces a metal for the base layer, in order to minimize base losses associated with scattering at the metal/semiconductor or base/collector interface. A contact structure is provided which makes selective low resistance contact to the thin base region. The contact structure is illustrated in Figs. 1, 2 and 3. The transistor type of interest (Fig. 1) consists of a InGaAs base sandwiched between two GaAs layers, which serve as emitter and collector. In Fig. 2, a detail of Fig. 1 is shown where a mesa, which defines the device, is etched so as to leave a sloping edge on which the various layers are exposed.