Seiichi Banba

Excellent Thermally Stable Epitaxial Channel for Implanted Planar-Type Heterojunction Field-Effect Transistors

We demonstrate for the first time that the decrease in the carrier concentration of highly doped GaAs layers caused by annealing is alleviated by thinning the layers. It is also suggested that the decrease is dependent on the Fermi energy in the doped layers. Thermally stable thin Si-doped GaAs channels are formed in implanted planar-type two-mode channel field-effect transistors (P-TMTs). A 0.2-μm device having a GaAs channel 9 nm thick with a doping level of 7 x 10 18 cm -3 exhibits excellent performance, such as a transconductance g m of 450 mS/mm, a current-gain cutoff frequency f T of 72 GHz, and a maximum frequency of oscillation f max of 140 GHz. Furthermore, it is indicated that highly doped thin layers are very effective for improving the DC and microwave performance of P-TMTs.