AlGaAs/InGaAs pseudomorphic doped channel field effect transistor with a P-AlAs buffer layer grown by metalorganic chemical vapor deposition

An AlAs buffer layer was successfully utilized in a 0.25-mu m-gate pseudomo rphic doped channel field effect transistor for the first time by growing a high quality p-AlAs layer by metalorganic chemical vapor deposition that a ttenuated the commonly observed roughness-induced degradation. Compared wit h a device containing a thick GaAs buffer layer alone, the RF g(m)/g(DS) ra tio and f(max) in this device were increased by 42% to 39 and by 19% to 160 GHz, respectively, at the expense of a slight decrease in g(m) and f(T). A s a result of the reduced leakage conduction through the buffer layer at hi gh temperatures, the fabricated doped channel FET with the p-AlAs buffer la yer was completely pinched off and it exhibited excellent DC current-voltag e characteristics even at elevated temperatures up to 200 degrees C.