IMPROVED P-CHANNEL INALAS GAASSB HIGFET USING TI/PT/AU OHMIC CONTACTSTO BERYLLIUM IMPLANTED GAASSB/

Ti/Pt/Au is demonstrated as an ohmic contact which provides a thermall y stable, low resistance, electrical interface to beryllium implanted GaAs1-xSbx on InP. Ohmic contacts are characterized electrically using the transmission line method. An extremely low contact resistance (rh o(c) < 3 x 10(-7) Omega . cm(2)) is measured for thermal processing te mperatures to T = 450 degrees C. The contact withstands an ambient tem perature of T = 250 degrees C for up to 500 h. Microstructural charact erization of the metal-semiconductor interface is achieved using Auger electron spectroscopy, X-ray diffraction and cross-sectional transmis sion electron microscopy. Contact sintering at T = 250 degrees C penet rates native oxides and minimizes contact resistance through formation of tunneling regions. Thermal degradation of the contact at T = 475 d egrees C results from Au indiffusion and Ga and Sb outdiffusion with a dditional formation of Ga3Pt5 and TiAu phases. A single metallization of Ti/Pt/Au is employed for the source, drain and gate of the In0.52Al 0.48As/GaAs0.51Sb0.49 p-channel heterostructure insulated-gate field e ffect transistor (HIGFET). Improvements are realized in the source/dra in contact reliability, external transconductance, output conductance and cutoff characteristics of the In0.52Al0.48As/GaAs0.51Sb0.49 HIGFET compared with previous designs using alloyed Au/Zn/Au source/drain co ntacts. External transconductance of g(me) = 5.3 mS/mm and an output c onductance of g(o) = 0.21 mS/mm are achieved on devices with gate leng th and width dimensions of L(G) = 1 mu m and W-G = 10 mu m, respective ly.