Effect of AlGaN Barrier Thickness on the Noise of AlGaN/GaN High Electron Mobility Transistors

ABSTRACTAlGaN/GaN HEMTs (High Electron Mobility Transistors) grown on semi-insulating (SI) SiC substrates are very promising for high power, high speed, and high temperature operation with great potential for both military and commercial applications. These high performance characteristics are possible due to presence of high two-dimensional electron gas (2 DEG) charge sheet density maintaining a high Hall mobility at the AlGaN barrier/GaN buffer hetero-interface. However, reliability of AlGaN HEMTs still remains a major concern because of the large number of defects and traps present both in the bulk as well as at the surface leading to current collapse. We report on the study of defects and surface properties in MOCVD-grown Al0.27Ga0.73N HEMT structures on SI SiC substrates. Our HEMT structures consist of a 25nm thick undoped AlGaN barrier layer and a 3μm thick undoped GaN buffer layer grown on a 100nm thick AlN nucleation layer. Hall measurements showed a charge sheet density of ∼1013/cm2 and a Hall mobility of ∼1500cm2/V·sec. Both cross-sectional and plan view TEMs were employed to study defects in the heterostructures and XPS (X-ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy) employed to study surface properties in both GaN and AlGaN layers. DC characterization results from AlGaN Schottky diodes with Pt/Au Schottky contacts are also reported along with results from AlGaN/GaN HEMT devices.

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AlGaN/GaN High Electron Mobility Transistors on Si/SiO2/poly-SiC Substrates

MRS Proceedings ◽

10.1557/proc-0955-i16-02 ◽

2006 ◽

Vol 955 ◽

Cited By ~ 1

Author(s):

Travis Anderson ◽

Fan Ren ◽

Lars Voss ◽

Mark Hlad ◽

Brent P Gila ◽

...

Keyword(s):

Electron Mobility ◽

High Electron Mobility Transistors ◽

Parameter Extraction ◽

High Electron ◽

High Electron Mobility ◽

Drain Spacing ◽

Electron Mobility Transistors ◽

Algan Barrier ◽

Rf Performance ◽

Spacing Parameter

ABSTRACTThe dc and rf performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs) grown by Molecular Beam Epitaxy on Si-on-poly (SopSiC) substrates is reported. The HEMT structure incorporated a 7 period GaN/AlN superlattice between the AlGaN barrier and GaN channel for improved carrier confinement. The knee voltage of devices with 2 μm gate-drain spacing was 2.12 V and increased to 3 V at 8 μm spacing. The maximum frequency of oscillation, fMAX, was ∼40 GHz for devices with 0.5 μm gate length and 2 μm gate-drain spacing. Parameter extraction from the measured rf characteristics showed a maximum intrinsic transconductance of 143 mS.mm−1.

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Variation of Dominant Degradation Mechanism in AlGaN Barrier Layer With Different Voltage Stress on the Gate of AlGaN/GaN High Electron Mobility Transistors

IEEE Electron Device Letters ◽

10.1109/led.2015.2399774 ◽

2015 ◽

Vol 36 (4) ◽

pp. 321-323 ◽

Cited By ~ 5

Author(s):

Lei Shi ◽

Shiwei Feng ◽

Yamin Zhang ◽

Bangbing Shi ◽

Kun Liu

Keyword(s):

Barrier Layer ◽

Electron Mobility ◽

Degradation Mechanism ◽

High Electron Mobility Transistors ◽

High Electron ◽

High Electron Mobility ◽

Electron Mobility Transistors ◽

Algan Barrier ◽

Voltage Stress ◽

Algan Barrier Layer

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Traps and Defects in AlGaN-GaN High Electron Mobility Transistors on Semi-Insulating SiC Substrates

MRS Proceedings ◽

10.1557/proc-1202-i09-02 ◽

2009 ◽

Vol 1202 ◽

Author(s):

Yongkun Sin ◽

Erica Deionno ◽

Brendan Foran ◽

Nathan Presser

Keyword(s):

Hall Mobility ◽

Electron Mobility ◽

Schottky Diodes ◽

High Electron Mobility Transistors ◽

High Electron ◽

Plan View ◽

High Electron Mobility ◽

Electron Mobility Transistors ◽

Algan Barrier ◽

Sheet Density

AbstractHigh electron mobility transistors (HEMTs) based on AlGaN-GaN hetero-structures are promising for high power, high speed, and high temperature operation. Especially, AlGaN-GaN HEMTs grown on semi-insulating (SI) SiC substrates are the most promising for both military and commercial applications. High performance characteristics from these devices are possible in part due to the presence of high two-dimensional electron gas charge sheet density maintaining a high Hall mobility at the AlGaN barrier-GaN buffer hetero-interface and in part due to high thermal conductivity of the SiC substrates. However, long-term reliability of these devices still remains a major concern because of the large number of traps and defects present both in the bulk as well as at the surface leading to undesirable characteristics including current collapse. We report on the study of traps and defects in two MOCVD-grown structures: Al0.27Ga0.73N HEMTs on SI SiC substrates and Al0.27Ga0.73N Schottky diodes on conducting SiC substrates. Our HEMT structures consisting of undoped AlGaN barrier and GaN buffer layers grown on an AlN nucleation layer show a charge sheet density of ∼1013/cm2 and a Hall mobility of ∼1500cm2/V·sec. Deep level transient spectroscopy (DLTS) was employed to study traps in AlGaN Schottky diodes and HEMTs fabricated with different Schottky contacts consisting of Pt/Au and Ni/Au. Focused ion beam was employed to prepare both cross-sectional and plan view TEM samples for defect analysis using a high resolution TEM.

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