AlGaN/GaN HEMTs on Semi-Insulating GaN Substrates by MOCVD and MBE

Silicon Si implantation into AIGaNGaN high electron mobility transistors HEMTs has been studied in this program as a method to reduce the sharp increase in the dynamic source resistance at increasing current levels that result in a reduction both in the transconductance gm and the current gain cut-off frequency fT. During the program two different approaches have been investigated to decrease the electric field in the source access region. To prevent breakdown between source and gate, different barrier layers have been investigated. Ultimately, these barriers allow an overlap between the gate and the source implant region. First, a regrown AIGaNGaN channel as the barrier between the source implant region and the gate has been investigated. In the past, silicon has been found to create a buried parasitic layer conductive path at the re-grown interface. In this work, multiple-cycle treatment with hydrofluoric acid and ozone was used to reduce the silicon at the regrowth interface by 80. Second, using silicon nitride SiN as the barrier layer between the implanted source region and the gate allowed a regrowth free structure. MOCVD grown SiN was deposited in situ after the activation anneal of the implanted silicon. With channels lengths down to 0.3 jam and gate lengths of 200 nm, these devices exhibited constant dynamic source resistances which improved the transconductance linearity at high current levels significantly.