Improved [formula omitted] higfet using Ti/Pt/Au ohmic contacts to beryllium implanted GaAsSb

Abstract

Ti/Pt/Au is demonstrated as an ohmic contact which provides a thermally stable, low resistance, electrical interface to beryllium implanted GaAs 1− x Sb x on InP. Ohmic contacts are characterized electrically using the transmission line method. An extremely low contact resistance ( ϱ c < 3 × 10 −7 Ω· cm 2 ) is measured for thermal processing temperatures to T = 450°C. The contact withstands an ambient temperature of T = 250°C for up to 500 h. Microstructural characterization of the metal-semiconductor interface is achieved using Auger electron spectroscopy, X-ray diffraction and cross-sectional transmission electron microscopy. Contact sintering at T = 250°C penetrates native oxides and minimizes contact resistance through formation of tunneling regions. Thermal degradation of the contact at T = 475°C results from Au indiffusion and Ga and Sb outdiffusion with additional formation of Ga 3Pt 5 and TiAu phases. A single metallization of Ti/Pt/Au is employed for the source, drain and gate of the In 0.52 Al 0.48 As GaAs 0.51 Sb 0.49 p- channel heterostructure insulated-gate field effect transistor (HIGFET). Improvements are realized in the source/drain contact reliability, external transconductance, output conductance and cutoff characteristics of the In 0.52 Al 0.48 As GaAs 0.51 Sb 0.49 HIGFET compared with previous designs using alloyed Au/Zn/Au source/drain contacts. External transconductance of g me = 5.3 mS/mm and an output conductance of g 0 = 2.21 mS/mm are achieved on devices with gate length and width dimensions of L G = 1 μm and W G = 10 μm, respectively.