High performance refractory gate self-aligned GaAs MESFETs fabricated by arsine ambient rapid thermal annealing

We have applied arsine ambient rapid thermal annealing (RTA) to the fabrication of high-performance refractory gate self-aligned GaAs MESFETs. This has allowed us to take advantage of some of the strong points of rapid thermal annealing for these devices (reduced dopant movement and gate-channel interaction) without the difficulties of capped RTA (decapping problems, cap thermal-mismatch-stress driven dopant movement and gate-channel interaction) or the uncertain As loss characteristics of uncapped or proximity RTA. Using this technique we have fabricated self-aligned 0.8 micron gate length MESFETs with 50 nm epitaxially-grown channels of 2 × 10¹⁸/cm³nominal doping with -0.14 V threshold voltage, k-factor as large as 590 mS/V-mm, maximum transconductance over 550 mS/mm, and over 350 mA/mm current drive capability. We have also fabricated fully-ion-implanted devices using arsine ambient annealing for both the channel and self-aligning n+ implant anneals. For²⁹Si 30 KeV channel implants and²⁹Si 40 KV self-aligning implants we have achieved a k-factor as large as 610 mS/V-mm for a gate length of 0.6 micron. This k-factor is the largest reported for a GaAs MESFET (disregarding anomalous values for devices with hole injection and/or carrier multiplication effects).