Ultra-wide-bandgap AlGaN homojunction tunnel diodes with negative differential resistance

Evan A. Clinton, Zachary Engel, Ehsan Vadiee, Joe V. Carpenter, Zachary Holman, W. Alan Doolittle

Research output: Contribution to journalArticle

Abstract

The power efficiencies of state-of-the-art AlxGa1-xN deep-ultraviolet (UV) emitters operating in the <300 nm wavelength region are currently limited to a few percent in part due to limitations in the series and contact resistance which result in excessive drive voltages. AlxGa1-xN tunnel contacts and tunnel junctions in deep-UV devices are a promising route toward increasing these efficiencies by improving the contact resistances, hole injection, and reducing optical absorption by removing undesirable p-GaN contact layers. However, due to doping inefficiencies, standalone tunnel diodes have not been realized in the form of homojunction AlxGa1-xN. In this work, AlxGa1-xN (0.19 ≤ x ≤ 0.58) homojunction tunnel diodes are fabricated with high reverse bias current densities, and one device with x = 0.19 demonstrates a negative differential resistance at ∼2.4 V. AlxGa1-xN p++/n++/n tunnel diodes are compared to reference p++/i/n diodes to provide clarity about the role of tunneling conduction vs leakage conduction. Transmission electron microscopy verifies that heavy doping does not result in visible defects such as Mg precipitates and allows for subsequent epitaxy, critical for buried tunnel junction structures. Increasing the bandgap energy of AlxGa1-xN for higher Al content tunnel junctions decreases the tunnel current, but still allows sufficient conduction necessary for future improvements in deep UV emitter efficiencies.

Original languageEnglish (US)
Article number082104
JournalApplied Physics Letters
Volume115
Issue number8
DOIs
StatePublished - Aug 19 2019

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tunnel diodes
homojunctions
tunnel junctions
contact resistance
conduction
tunnels
emitters
p-i-n diodes
clarity
power efficiency
epitaxy
precipitates
optical absorption
leakage
routes
injection
current density
transmission electron microscopy
defects
electric potential

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Clinton, E. A., Engel, Z., Vadiee, E., Carpenter, J. V., Holman, Z., & Doolittle, W. A. (2019). Ultra-wide-bandgap AlGaN homojunction tunnel diodes with negative differential resistance. Applied Physics Letters, 115(8), [082104]. https://doi.org/10.1063/1.5113503

Ultra-wide-bandgap AlGaN homojunction tunnel diodes with negative differential resistance. / Clinton, Evan A.; Engel, Zachary; Vadiee, Ehsan; Carpenter, Joe V.; Holman, Zachary; Doolittle, W. Alan.

In: Applied Physics Letters, Vol. 115, No. 8, 082104, 19.08.2019.

Research output: Contribution to journalArticle

Clinton, Evan A. ; Engel, Zachary ; Vadiee, Ehsan ; Carpenter, Joe V. ; Holman, Zachary ; Doolittle, W. Alan. / Ultra-wide-bandgap AlGaN homojunction tunnel diodes with negative differential resistance. In: Applied Physics Letters. 2019 ; Vol. 115, No. 8.
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