A p-well GaAs MESFET technology for mixed-mode applications

A device structure consisting of an ion-implanted n-channel buried between an implanted p^- region at the surface and an implanted p-region under the channel is presented. The deep p-layer (p-well) is extended beyond the source region of the MESFET and independently contacted through an ohmic p⁺ diffusion. In normal operation, the source and p-well (backgate) terminals are electrically shorted together, as in silicon CMOS technology. By using junction isolation rather than conventional resistive isolation, the p-well n-channel MESFETs are free of trap-related parasitic effects including drain current transients with very long time constants, low-frequency frequency-dependent small-signal drain conductance, sidegating between neighboring devices, light sensitivity, etc. While eliminating these classical MESFET problems, the radiofrequency performance of the p-well GaAs MESFET remains comparable to the conventional n-channel device