Heo Jun-Woo, Kim Young-Jin, Kim Hyun-Seok
J Nanosci Nanotechnol. 2014 Dec;14(12):9436-42. doi: 10.1166/jnn.2014.10149.
We report two approaches to fabricating high performance normally-off AIGaN/GaN high-electron mobility transistors (HEMTs). The fabrication techniques employed were based on recessed-metal-insulator-semiconductor (MIS) gate and recessed fluoride-based plasma treatment. They were selectively applied to the area under the gate electrode to deplete the two-dimensional electron gas (2-DEG) density. We found that the recessed gate structure was effective in shifting the threshold voltage by controlling the etching depth of gate region to reduce the AIGaN layer thickness to less than 8 nm. Likewise, the CF4 plasma treatment effectively incorporated negatively charged fluorine ions into the thin AIGaN barrier so that the threshold voltage shifted to higher positive values. In addition to the increased threshold voltage, experimental results showed a maximum drain current and a maximum transconductance of 315 mA/mm and 100 mS/mm, respectively, for the recessed-MIS gate HEMT, and 340 mA/mm and 330 mS/mm, respectively, for the fluoride-based plasma treated HEMT.
我们报告了两种制造高性能常关型氮化铝镓/氮化镓高电子迁移率晶体管（HEMT）的方法。所采用的制造技术基于凹槽金属-绝缘体-半导体（MIS）栅极和基于氟化物的凹槽等离子体处理。它们被选择性地应用于栅电极下方的区域，以耗尽二维电子气（2-DEG）密度。我们发现，凹槽栅极结构通过控制栅极区域的蚀刻深度以将氮化铝镓层厚度减小到小于8nm，从而有效地移动阈值电压。同样，CF4等离子体处理有效地将带负电荷的氟离子掺入薄的氮化铝镓势垒中，使得阈值电压向更高的正值移动。除了阈值电压增加之外，实验结果表明，对于凹槽-MIS栅极HEMT，最大漏极电流和最大跨导分别为315 mA/mm和100 mS/mm，对于基于氟化物的等离子体处理的HEMT，分别为340 mA/mm和330 mS/mm。
