Adjustment of threshold voltage in AlN/AlGaN/GaN high-electron mobility transistors by plasma oxidation and Al2O3 atomic layer deposition overgrowth

作者：Gregusova D^*; Jurkovic M; Hascik S; Blaho M; Seifertova A; Fedor J; Tapajna M; Froehlich K; Vogrincic P; Liday J; Derluyn J; Germain M; Kuzmik J

来源：Applied Physics Letters, 2014, 104(1): 013506.

DOI：10.1063/1.4861463

We discuss possibilities of adjustment of a threshold voltage V-T in normally off GaN high-electron mobility transistors (HEMTs) without compromising a maximal drain current 1(DSmax). Techniques of a low power plasma or thermal oxidation of 2-nm thick AlN cap over 3-nm thick AlGaN barrier are developed and calibrated for a thorough oxidation of the cap with a minimal density of surface donors at the inherent oxide-semiconductor interface. It has been shown that while a thermal oxidation technique leads to the channel and/or interface degradation, low density of surface donors and scalability of V-T with additionally overgrown Al2O3 may be obtained for plasma oxidized HEMTs. With 10-nm thick Al2O3 deposited at 100 degrees C by atomic-layer deposition, we obtained V-T of 1.6V and 1(DSmax) of 0.48 A/mm at a gate voltage of V-GS = 8V. Density of surface donors was estimated to be about 1.2 x 10(13) cm(-2), leaving most of the negative polarization charge at the semiconductor surface uncompensated. Further reduction of surface donors may be needed for even higher V-T.

• 出版日期2014-1-6
• 单位中国科学院电工研究所