Surface‐Oxide‐Controlled InAlGaN/GaN High‐Electron‐Mobility Transistors Using Al₂O₃‐Based Insulated‐Gate Structures with H₂O Vapor Pretreatment

Abstract

Herein, Al2O3/InAlGaN/GaN metal–insulator–semiconductor high‐electron‐mobility transistors (MIS‐HEMTs) using H2O vapor pretreatment to decrease the amount of deficient indium oxide (InOx) is successfully developed. InOx acts as an electron trap in the oxide on the surface of the InAlGaN barrier layer. It is clarified that when O2 plasma is used as an oxidant source for atomic‐layer‐deposited (ALD) Al2O3 (O2 plasma‐Al2O3), the forward breakdown voltage increases using the MIS‐HEMT, due to a high density and a low leakage current of O2 plasma‐Al2O3. Furthermore, when using O2 plasma‐Al2O3 for InAlGaN/GaN MIS‐HEMTs, H2O vapor pretreatment is effective in decreasing the amount of InOx and electron traps in the oxide on the surface, thus suppressing current collapse. These results demonstrate the improved output power characteristics of the fabricated Al2O3/InAlGaN/GaN MIS‐HEMT and show the potential of surface‐oxide‐controlled MIS structures as promising process technologies for next‐generation high‐power radio frequency devices.

Surface-oxide-controlled InGaAs/InAlAs inverted-type metal-oxide-semiconductor high electron mobility transistors for sub-THz high-power amplifiers

“…We have previously reported that the improvement in the g m profile (the wider range of constant g m ) on InP-based HEMTs with a steam-annealed ultrathin-Al 2 O 3 gate dielectric (2 nm thick), due to a reduction in gate leakage current and an increase in forward breakdown voltage. 19) However, when using oxidant sources for ALD-Al 2 O 3 , the narrow band gap (∼3.4 eV) deficient indium oxide (InO x ) is generated in the surface-oxide of the In-based epitaxial layer, [20][21][22][23] thereby increasing the gate leakage current. 24) Thus, we developed inverted MOS-HEMTs with a surface-oxide-control (SOC) process that decreased the amount of InO x at the Al 2 O 3 /semiconductor interface.…”

Effect of oxidant sources on carbon-related impurities in ALD-Al2O3 for solid-state devices

“…ate leakage current in RF devices is one of the most important issues to be solved for application in highpower amplifiers. 1,2) Al 2 O 3 films are an attractive gate dielectric for RF devices such as high electron mobility transistors (HEMTs) because of their wide band gap (∼7.0 eV), high dielectric constant (∼9.0), and high breakdown voltage (∼10 MV cm −1 ). [3][4][5][6][7][8][9] Furthermore, it is necessary for RF devices to optimize the thickness of Al 2 O 3 films to suppress the gate leakage current and maximize transconductance simultaneously.…”

“…[3][4][5][6][7][8][9] Furthermore, it is necessary for RF devices to optimize the thickness of Al 2 O 3 films to suppress the gate leakage current and maximize transconductance simultaneously. 1,10) Thus, atomic layer deposited (ALD)-Al 2 O 3 is required for high-frequency RF devices, especially in sub-THz applications. [11][12][13] Furthermore, ALD-Al 2 O 3 is also used in advanced packaging such as surface-activated bonding (SAB) of heterogeneous wafers due to the thickness controllability for nano-adhesion layers and relatively high thermal conductivity.…”

Improved f T/f max in wide bias range by steam-annealed ultrathin-Al2O3 gate dielectrics for InP-based high-electron-mobility transistors

“…Thus, it is considered that the lattice disorder in bond lengths and angles 29) was induced by plasma damages at the surface of InGaP, leading to mobility degradation. 30) On the other hand, Al 2 O 3 gate dielectrics deposited by remote plasma ALD on the InGaP was effective to suppress these damages during SiN deposition. Therefore, R sh increase was suppressed by an insulated-gate HEMTs (SiN/Al 2 O 3 passivation), particularly after steam annealing (211 Ω/sq.…”

“…This effect is important in terms of the input dynamic range at forward bias for high-power RF devices. 30,31) The drain current versus drain voltage (I d -V d ) characteristics of an insulated-gate HEMT and Schottky-gate HEMT, are shown in Figs. 4(a) and 4(b), respectively.…”