J. Bude

GaN metal-oxide-semiconductor high-electron-mobility-transistor with atomic layer deposited Al2O3 as gate dielectric

We report on a GaN metal-oxide-semiconductor high-electron-mobility-transistor (MOS-HEMT) using atomic-layer-deposited (ALD) Al2O3 as the gate dielectric. Compared to a conventional GaN high-electron-mobility-transistor (HEMT) of similar design, the MOS-HEMT exhibits several orders of magnitude lower gate leakage and several times higher breakdown voltage and channel current. This implies that the ALD Al2O3∕AlGaN interface is of high quality and the ALD Al2O3∕AlGaN∕GaN MOS-HEMT is of high potential for high-power rf applications. In addition, the high-quality ALD Al2O3 gate dielectric allows the effective two-dimensional (2D) electron mobility at the AlGaN∕GaN heterojunction to be measured under a high transverse field. The resulting effective 2D electron mobility is much higher than that typical of Si, GaAs or InGaAs metal-oxide-semiconductor field-effect-transistors (MOSFETs).

GaAs MOSFET with oxide gate dielectric grown by atomic layer deposition

For the first time, a III-V compound semiconductor MOSFET with the gate dielectric grown by atomic layer deposition (ALD) is demonstrated. The novel application of the ALD process on III-V compound semiconductors affords tremendous functionality and opportunity by enabling the formation of high-quality gate oxides and passivation layers on III-V compound semiconductor devices. A 0.65-/spl mu/m gate-length depletion-mode n-channel GaAs MOSFET with an Al/sub 2/O/sub 3/ gate oxide thickness of 160 /spl Aring/ shows a gate leakage current density less than 10/sup -4/ A/cm/sup 2/ and a maximum transconductance of 130 mS/mm, with negligible drain current drift and hysteresis. A short-circuit current-gain cut-off frequency f/sub T/ of 14.0 GHz and a maximum oscillation frequency f/sub max/ of 25.2 GHz have been achieved from a 0.65-/spl mu/m gate-length device.

Depletion-mode InGaAs metal-oxide-semiconductor field-effect transistor with oxide gate dielectric grown by atomic-layer deposition

Recently, significant progress has been made on GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using atomic-layer deposition (ALD)-grown Al2O3 as gate dielectric. We show here that further improvement can be achieved by inserting a thin In0.2Ga0.8As layer as part of the channel between Al2O3 and GaAs channel. A 1-μm-gate-length, depletion-mode, n-channel In0.2Ga0.8As/GaAs MOSFET with an Al2O3 gate oxide of 160 A shows a gate leakage current density less than 10−4 A/cm2, a maximum transconductance ∼105 mS/mm, and a strong accumulation current at Vgs>0 in addition to buried-channel conduction. Together with longer gate-length devices, we deduce electron accumulation surface mobility for In0.2Ga0.8As as high as 660 cm2/V s at Al2O3/In0.2Ga0.8As interface.

Advances in high κ gate dielectrics for Si and III-V semiconductors

Abstract Our ability of controlling the growth and interfaces of thin dielectric films on III–V semiconductors by ultrahigh vacuum deposition has led to investigations of gate stacks containing rare earth oxides of Gd 2 O 3 and Y 2 O 3 as alternative high κ gate dielectrics for Si. The abrupt interfaces achieved in these gate stacks have enabled the electrical, chemical, and structural studies to elucidate the critical materials integration issues for CMOS scaling, including morphology dependence, interfacial structure and reaction, thermal stability and gate electrode compatibility.

GaN MOS-HEMT USING ATOMIC LAYER DEPOSITION Al2O3 AS GATE DIELECTRIC AND SURFACE PASSIVATION

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic layer deposition (ALD) Al2O3 film as a gate dielectric and for surface passivation simultaneously. Compared to the conventional AlGaN/GaN HEMT of the same design, six order of magnitude smaller gate leakage current and tripled drain current at forward gate bias demonstrate the effectiveness of ALD Al2O3 as a gate dielectric. The high transconductance and high effective two-dimensional electron mobility verify the high-quality of Al2O3/AlGaN interface with low interface trap density. The Al2O3 passivation effect is also studied by sheet resistance measurement and short pulse drain characterization.

Minimizing gate lag of a planar high-power GaAs MESFET by Al/sub 2/O/sub 3/ passivation and optimized gate process

This study demonstrates that using ALD grown Al/sub 2/O/sub 3/ as a surface passivation layer, and by controlling the Al/sub 2/O/sub 3/ over-etch time, the gate lag of a planar high power GaAs MESFET can be controlled to an undetectable level. In addition, more than 30 V higher Vbkd was achieved when the Al/sub 2/O/sub 3/ surface passivation layer was employed. These results indicate that the above reported GaAs MESFET device is very promising for wireless base station high-power amplifier applications.

DC and RF characteristics of depletion-mode GaAs MOSFET employing a thin Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) gate dielectric layer

DC characteristics of a depletion-mode (D-mode) GaAs MOSFET with a thin Ga/sub 2/O/sub 3/(Gd/sub 2/O/sub 3/) gate dielectric layer (74 /spl Aring/) show low gate leakage current, negligible drain current hysteresis and higher than 10 V gale-drain two-terminal breakdown voltage. Compared to MESFET with the same gate length, channel material and fabricated by the same process, the GaAs MOSFET shows higher unity current gain cutoff frequency (Ft). The higher Ft for the MOSFET than that of the MESFET agrees with earlier theoretical predictions.

GaN MOS-HEMT using atomic layer deposition Al/sub 2/O/sub 3/ as gate dielectric and surface passivation

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic layer deposition (ALD) Al/sub 2/O/sub 3/ film as a gate dielectric and for surface passivation simultaneously. Compared to the conventional AlGaN/GaN HEMT of the same design, six order of magnitude smaller gate leakage current and tripled drain current at forward gate bias demonstrate the effectiveness of ALD Al/sub 2/O/sub 3/ as a gate dielectric. The high transconductance and high effective two-dimensional electron mobility verify the high-quality of Al/sub 2/O/sub 3//AlGaN interface with low interface trap density. The Al/sub 2/O/sub 3/ passivation effect is also studied by sheet resistance measurement and short pulse drain characterization.

GaAs-based MOSFETs with Al/sub 2/O/sub 3/ gate dielectrics grown by atomic layer deposition

In this paper, we demonstrate for the first time GaAs-based MOSFETs with excellent performance using of CVD is a very robust, highly manufacturable process.