Study of GaN MOS-HEMT using ultrathin Al2O3 dielectric grown by atomic layer deposition

Abstract

Citation: Yue Y Z, Hao Y, Feng Q, et al. Study of GaN MOS-HEMT using ultrathin Al 2 O 3 dielectric grown by atomic layer deposition.We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic-layer deposited (ALD) Al 2 O 3 as the gate dielectric. Through further decreasing the thickness of the gate oxide to 3.5 nm and optimizing the device fabrication process，a device with maximum transconductance of 150 mS/mm was produced. The drain current of this 0.8 μm gate-length MOS-HEMT could reach 800 mA/mm at +3.0 V gate bias. Compared to a conventional AlGaN/GaN HEMT of similar design, better interface property, lower leakage current, and smaller capacitance-voltage (C-V) hysteresis were obtained, and the superiority of this MOS-HEMT device structure with ALD Al 2 O 3 gate dielectric was exhibited.

AlGaN/GaN hybrid MOS-HEMT analytical mobility model

“…It has been calculated the R on for an hybrid MOS-HEMT (L G = 1 lm l MOS = 50 cm 2 /V s) for SiO 2 and different common high-k dielectrics. The dielectric constant is 7.4, 10 and 20 for SiN x , Al 2 O 3 and HfO 2 , respectively [20][21][22]. For a given gate insulator thickness the lower on-resistance is achieved for the dielectrics with the higher dielectric constant.…”

Effect of GaN surface treatment on Al2O3/n-GaN MOS capacitors

“…In selecting the gate oxide, a band offset larger than 1 eV is needed to suppress leakage currents. 6 In this respect, Al 2 O 3 is an excellent high-j dielectric, due to its high permittivity (8)(9)(10), large bandgap (8.9 eV), and high energy conduction band edge offset with GaN [2.13 eV (Ref.…”

“…8 The major obstacle to using Al 2 O 3 deposited on III-V semiconductors is its high-interface trap density (D it > 10 13 cm…”

AlGaN/GaN MOS-HEMT with Stack Gate HfO2/Al2O3 Structure Grown by Atomic Layer Deposition

“…Significant progress has been made on GaN/AlGaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) using SiO 2 [1], Si 3 N 4 [2], Ga 2 O 3 [3], Al 2 O 3 [4][5][6] and Sc 2 O 3 [7] as the gate dielectrics to suppress the above-mentioned problems but at the expense of a significant decrease in device transconductance [4] and a large threshold voltage shift [5][6]. Usage of dielectrics with high permittivity (high k) could help solve these problems, because larger dielectric constant could translate to more efficient gate modulation [8], thus a smaller decrease in transconductance and a moderate increase in the threshold voltage could be expected in MOS-HEMTs with high-k gate dielectrics.…”

“…Recently, we have demonstrated a novel GaN/AlGaN MOS-HEMT using ultrathin Al 2 O 3 dielectric of 3.5nm grown by ALD which has good passivation effect and low interface state [5][6]. Al 2 O 3 has better thermal stability (amorphous up to at least 1000 °C) and chemical stability against AlGaN than HfO 2 [4,9] which makes Al 2 O 3 a good candidate for IPL application for high k gate MOS-HEMT fabrication.…”