Comparative study on characteristics of Si-based AlGaN/GaN recessed MIS-HEMTs with HfO₂ and Al₂O₃ gate insulators*

Abstract

Two types of enhancement-mode (E-mode) AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) with different gate insulators are fabricated on Si substrates. The HfO2 gate insulator and the Al2O3 gate insulator each with a thickness of 30 nm are grown by the plasma-enhanced atomic layer deposition (PEALD). The energy band diagrams of two types of dielectric MIS-HEMTs are compared. The breakdown voltage (V BR) of HfO2 dielectric layer and Al2O3 dielectric layer are 9.4 V and 15.9 V, respectively. With the same barrier thickness, the transconductance of MIS-HEMT with HfO2 is larger. The threshold voltage (V th) of the HfO2 and Al2O3 MIS-HEMT are 2.0 V and 2.4 V, respectively, when the barrier layer thickness is 0 nm. The C–V characteristics are in good agreement with the V th’s transfer characteristics. As the barrier layer becomes thinner, the drain current density decreases sharply. Due to the dielectric/AlGaN interface is very close to the channel, the scattering of interface states will lead the electron mobility to decrease. The current collapse and the R on of Al2O3 MIS-HEMT are smaller at the maximum gate voltage. As Al2O3 has excellent thermal stability and chemical stability, the interface state density of Al2O3/AlGaN is less than that of HfO2/AlGaN.

DC and RF performance analysis of enhancement mode fin-shaped tri-gate AlGaN/GaN HEMT and MOSHEMT with ultra-thin barrier layer

“…To overcome poor device performance, like GVS and quasi normally-off (E-mode) behavior in ultrathin AlGaN barrier HEMTs, the insertion of several gate dielectric materials like SiO 2 , Si 3 N 4 , Al 2 O 3, and HfO 2 between the Schottky metal gate and AlGaN barrier have been proposed previously [29][30][31][32]. Among these, atomic layer deposition (ALD) of high-k dielectric materials, in particular Al 2 O 3 , has shown better performance in the reduction of gate leakage current and minimum current collapse with improved V T towards E-mode operation in barrier-scaled AlGaN/GaN MOSHEMTs [33]. However, insertion of high-k gate dielectric in conventional AlGaN/GaN MOSHEMT is found to impact V T (shifts threshold voltage negatively) due to the combined effects of increased Schottky gate to 2DEG channel separation, trapped charge density at the oxide and AlGaN interface states (N it ) [31] and positively charged barrier surface donors density (N DS ) below the gate [34].…”

Ferroelectric effect and equivalent polarization charge model of PbZr0.2Ti0.8O3 on AlGaN/GaN MIS-HEMT*

“…In the test, the pulse width is 5 × 10 −7 s, with 1-ms period and 1.5 × 10 −7 -s rise time and the decline time. [18] The current collapse test selects two static operating points, the (V gs , V ds ) = (0, 0) state and the (V gs , V ds ) = (−8, 10) state. According to the measurement, the current collapse of the MIS-HEMT is 5.2%.…”

Heterogeneous integration of high-k complex-oxide gate dielectrics on wide band-gap high-electron-mobility transistors

“…To further improve the performance and reliability beyond conventional GaN HEMTs with Schottky metal gate, metal-oxide-semiconductor (MOS)-HEMTs structures have been proposed to suppress gate leakage and passivated the GaN surface from ambient. In this regard, MOS-GaN HEMTs with various dielectric materials such as Al 2 O 3 and HfO 2 have been demonstrated 12 – 14 . In MOS-HEMT, the crystallization and interfacial quality of the gate dielectric material play a crucial role in determining the performance 15 .…”