Narrow-channel GaInP/InGaAs/GaAs MODFETs for high-frequency and power applications

We have developed a new concept of narrow (50-80 Å) channel MODFETs. It is shown theoretically and experimentally that only the ground energy level is populated in the narrow-channel device. A new technique to measure mobility at the highest energies of the two-dimensional electron gas (2-DEG) was introduced. With the help of this technique it is shown that, in wide wells, electrons in the excited energy levels have low mobility and consequently degrade device performance. It is shown theoretically and experimentally that the narrow-channel device has a higher electron sheet density and mobility and consequently better performance than a conventional wide-channel MODFET. Excellent quality Ga_xIn_1-xP/In_yGa_1-yAs/GaAs MODFETs with a pseudomorphic barrier and a pseudomorphic channel were grown by MBE and OMVPE. Higher than 3.4·10¹² cm^-2 electron sheet densities for single-side-doped MODFETs on GaAs substrate were measured. One-tenth micron gate length MODFETs achieved f _T´s over 100 GHz and f_max´s over 180 GHz. These results are comparable to the previously reported results for GaInP MODPET with graded barriers, however the device structure is much simpler