Suppression of Mg Propagate into Subsequent Layers by Furnace Annealing

Abstract

Multilayers and trench MOS structures have been involved to investigate the diffusion behavior of Mg atoms and the corresponded electrical properties. Four groups of p-n + stacked layers were grown to study the effect of different interfacial treatment. The growth conditions of these four groups were identical except for different interfacial treatment during the growth, including as grown, furnace annealing, AlGaN interlayer and furnace annealing with AlGaN interlayer. Furnace annealing refers to 850°C for 10 min in a nitrogen atmosphere in MOCVD and AlGaN interlayer means a 50 nm Si-doped $\text{Al}_{0.08}\text{Ga}_{0.92}\mathrm{N}$ layers have been inserted. The slope of the Mg concentration for the furnace annealing sample is 90 s/dec-less than 63% of the as-grown sample. SIMS results also reveals that furnace annealing introduce an interface with a low conductivity while an improved sheet resistance of subsequent n + layer from 630 Ω/Ÿ to 415 Ω/Ÿ. Especially, the sum of resistance, including the drain and source contact resistance, contact layer resistance (RS and RD) and channel resistance (RCH), decreased from 151.5 Ω.mm to 125.9 Ω.mm via furnace annealing which has been verified by quasi-vertical n+-p-unintentionally doped (n+-p-uid) GaN-on-GaN trench MOS structure with different trench width. Furnace annealing has been successfully used to prevent Mg atoms from Metalorganic Chemical Vapor Deposition (MOCVD) grown p-GaN:Mg layers riding into subsequently deposited n+-type layer and improve the electrical characteristic of sheet resistance and ON-resistance in the device of trench MOS structure. This work shows a great reference value for GaN with a buried p-GaN structure.