Influence of channel doping-profile on camel-gate field effect transistors

We report the performance of GaAs camel-gate FET's and its dependence on device parameters, In particular, the performance dependence on the doping-profile of a channel was investigated, In this study, one-step, bi-step, and tri-step doping channels with the same doping-thickness product are employed in camel-gate FET's, while keeping other parameters unchanged, For a one-step doping channel FET, theoretical analysis reveals that a high doping channel would provide a large transconductance which is suitable for logic applications. Decreasing the channel concentration increases the drain current and the barrier height. For a tri-step doping channel FET, it is found that the output drain current and the barrier height remain large and the relatively voltage-independent transconductance is also increased, These are the requirements for the large input signal power amplifiers, A fabricated camel-gate FET with a tri-step doping channel exhibits a large drain current density larger than 750 mA/mm and a potential barrier greater than 1.0 V. Furthermore, the relatively voltage-independent transconductance is as high as 220 mS/mm and the applied gate voltage is up to +1.5 V. A 1.5 x 100 mu m(2) device is found to have a f(t) of 30 GHz with a very low input capacitance.