High Al-Content AlGaN Transistor With 0.5 A/mm Current Density and Lateral Breakdown Field Exceeding 3.6 MV/cm

Bajaj, Sanyam; Allerman, Andrew A.; Armstrong, Andrew M.; Razzak, Towhidur; Talesara, Vishank; Sun, Wenyuan; Sohel, Shahadat H.; Zhang, Y.; Lu, Wu; Arehart, Aaron R.; Akyol, Fatih; Rajan, Siddharth

doi:10.1109/led.2017.2780221

Cited by 50 publications

(29 citation statements)

References 24 publications

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“…For Sample A (Figure 1(a)), the contact layer was graded from x=0.7 to x=0 over 50 nm, like previous reports, which requires [Si + ] > 8×10 18 cm -3 for polarization charge compensation ( Figure 1(b)). 22,23 For sample B (Figure 1(c)), the Al-composition was graded from x=0.7 to x=0.3 over 150 nm such that a lower [Si + ] concentration, can compensate the negative polarization charge density (Figure 1(d)). While a lower x at the top surface of the contact layer yields a lower metal-semiconductor resistance, the contact layer resistance will be higher due to a higher negative polarization charge density due to larger compositional grading and vice versa.…”

Section: Usamentioning

confidence: 99%

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Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors

Hwang

Coleman

Han

et al. 2019

Applied Physics Letters

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In this letter, we design and demonstrate an improved MOCVD grown reverse Al-composition graded contact layer to achieve low resistance contact to MOCVD grown ultra-wide bandgap (UWBG) Al 0.70 Ga 0.30 N channel metalsemiconductor field-effect transistors (MESFETs). Increasing the thickness of the reverse graded layer was found to improve contact layer resistance significantly, leading to contact resistance of 3.3×10 -5 Ω·cm 2 . Devices with gate length, L G , of 0.6 µm and source-drain spacing, L SD , of 1.5 µm displayed a maximum current density, I DS,MAX , of 635 mA/mm with an applied gate voltage, V GS , of +2 V. Breakdown measurements on transistors with gate to drain spacing, L GD , of 770 nm had breakdown voltage greater than 220 , corresponding to minimum breakdown field of 2.86 MV/cm. This work provides a framework for the design of low resistance contacts to MOCVD grown high Al-content Al x Ga 1-x N channel transistors.

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Section: Usamentioning

confidence: 99%

“…can be further improved by the addition of a gate dielectric such as Al 2 O 3 22. In summary, we have designed and demonstrated an improved MOCVD grown Al-composition graded contact layer with a contact resistance of 3.3×10 -5 Ω·cm 2 -lowest for MOCVD grown Al x Ga 1-x N channel transistor with x > 0.5.…”

mentioning

confidence: 95%

Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors

Hwang

Coleman

Han

et al. 2019

Applied Physics Letters

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“…Despite achieving ohmic contacts, the I ds,max value for the PolFET is lower than the best previous reports for UWBG AlGaN HEMTs 2,3,9,10) and MESFETs. [14][15][16] Lower I ds,max for the PolFET is due in part to a larger source-to-drain spacing but primarily to a lower Al contrast in the heterostructure that results in a higher R sh and smaller knee voltage. Nonetheless, the PolFET compares well against prior HEMT and MESFET results in important aspects.…”

Section: Polfet Comparison To Hemts and Mesfetsmentioning

confidence: 99%

“…6,12,13) However, achieving ohmic contacts and simultaneously high μ and sheet density (n s ) remain significant challenges for AlGaN transistors. Al x Ga 1−x N metal-semiconductor field effect transistors (MESFETs) with ohmic source and drain contacts have been demonstrated for x = 0.65, 14) and 0.70, 15,16) but μ has yet to exceed 100 cm 2 V −1 s −1 for devices with current density >100 mA=mm. Channel μ of highly conductive UWBG Al x Ga 1−x N MESFETs is likely to remain <100 cm 2 V −1 s −1 because significant improvement requires increasing x > 0.8 to reduce alloy scattering, 5,17) but n-type impurity doping becomes inefficacious for x > 0.8.…”

Section: Introductionmentioning

confidence: 99%

Ultra-wide band gap AlGaN polarization-doped field effect transistor

Armstrong

Klein

Colon

et al. 2018

Jpn. J. Appl. Phys.

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Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped Al x Ga 1%x N channel layer graded over Al compositions 0.70 : x : 0.85 and ohmic contact formation to the Al 0.85 Ga 0.15 N surface. Current density of 24 mA/mm was attained for a modest threshold voltage of %3.95 V owing to the high sheet charge concentration (n s) of 5.4 ' 10 12 cm %2 and average electron mobility (μ) of 210 cm 2 V %1 s %1 for the channel region along with ohmic contacts with a specific contact resistivity of 1.1 mΩ cm 2 and a large Schottky barrier height of 3.0 eV for the metal-semiconductor gate. The combination of ultra-wide band gap energy, high μ, and high n s , linear ohmic contacts, and large Schottky barrier for AlGaN PolFETs makes them attractive for both high voltage switches and high power rf devices.

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“…In addition to field plates engineering, Schottky drain contacts, lightly doped drain, recessed gate edge, and floating metal ring were also found to increase the breakdown voltage. Currently, to push the breakdown voltage further, high Al composition AlGaN channels are being investigated . Here, we report a novel approach to increase the breakdown voltage by engineering the gate edge (meandering) toward drain.…”

Section: Introductionmentioning

confidence: 99%

Meandering Gate Edges for Breakdown Voltage Enhancement in AlGaN/GaN High Electron Mobility Transistors

Kumar

Dolmanan

Tripathy

et al. 2020

Physica Status Solidi (a)

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Herein, a unique device‐design strategy is reported for increasing the breakdown voltage and hence Baliga figure of merit (BFOM) of III‐nitride high electron mobility transistors (HEMTs) by engineering the gate edge toward the drain. The breakdown of such devices with meandering gate‐drain access region (M‐HEMT) are found to be 62% more compared with that of conventional HEMT whereas the on‐resistance suffers by 76%, leading to an overall improvement in the BFOM for by 28%. The 3D technology computer‐aided design simulations show that the decrease in the peak electric field at the gate edge was responsible for increased breakdown voltage.

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High Al-Content AlGaN Transistor With 0.5 A/mm Current Density and Lateral Breakdown Field Exceeding 3.6 MV/cm

Cited by 50 publications

References 24 publications

Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors

Design of compositionally graded contact layers for MOCVD grown high Al-content AlGaN transistors

Ultra-wide band gap AlGaN polarization-doped field effect transistor

Meandering Gate Edges for Breakdown Voltage Enhancement in AlGaN/GaN High Electron Mobility Transistors

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