An Ultrathin AlGaN Barrier Layer MIS-HEMT Structure for Enhancement-Mode Operation
QUAN Si1, MA Xiao-Hua2, ZHENG Xue-Feng3, HAO Yue3**
1School of Electronics and Control Engineering, Chang'an University, Xi'an 710064 2School of Technical Physics, Xidian University, Xi'an 710071 3Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, Xidian University, Xi'an 710071
Abstract：A GaN-based enhancement-mode (E-Mode) metal-insulator-semiconductor (MIS) high electron mobility transistor (HEMT) with a 2 nm/5 nm/1.5nm-thin GaN/AlGaN/AlN barrier is presented. We find that the formation of a two-dimensional electron gas (2DES) in the GaN/AlGaN/AlN/GaN heterostructure can be controlled by the presence of the plasma-enhanced chemical-vapor deposition (PECVD) Si3N4 on the barrier layer, and the degree of decrease in sheet resistance Rsh is dependent on the Si3N4 thickness. We choose 13 nm Si3N4 as the gate insulator to decrease gate current and to improve the threshold voltage of devices. With selective etching of the passivation Si3N4 under gate and over fluorine plasma treatment, the MIS-HEMT exhibits a high threshold voltage of 1.8 V. The maximum drain current Id,max and the maximum transconductance are 810 mA/mm and 190 mS/mm, respectively. The devices show a wide operation range of 4.5 V.
2013, Vol. 30 
