Electrical contact considerations for diamond electron emission diodes

Franz A. Koeck, Manpuneet Benipal, Robert J. Nemanich

Research output: Contribution to journalArticle

Abstract

The demonstration of diamond devices has substantiated the superior capability of diamond in high power electronics that relied on the preparation of p-type and n-type diamond through boron and phosphorus doping, respectively, and the growth of high purity intrinsic diamond. We present an approach for electrical contacts to homoepitaxial, phosphorus doped, n-type, diamond that utilizes an interfacial layer of highly nitrogen doped, nanostructured carbon grown by plasma enhanced CVD (PECVD). This contact strategy was utilized in a pin diamond diode for electron source applications. The pin-nano-carbon structure was prepared on HPHT type IIb (111) oriented substrates with intrinsic, n-type, and nano-carbon layer grown in dedicated PECVD systems. The nanostructured nitrogen doped carbon layer was synthesized under argon addition to promote re-nucleation. Diodes from this pin-nano-carbon structure were prepared by lithography and mesa-etched devices contacted by Ti/Pt/Au metallurgy. Final processing in a hydrogen plasma established negative electron affinity properties for electron emission. Electrical characterization of the diodes commenced in vacuum after annealing at ~600 °C for 15 min and observation of exciton light emission indicated bipolar transport. At a forward bias of 14 V a current of 0.1A was measured and at 17 V its increase to 0.5A corresponded to a current density >1500 A/cm2. Compared to conventional pin diodes, the introduction of the nano-carbon layer enhanced the diode and electron emission current by more than an order of magnitude. This was attributed to the reduced contact resistivity of 5.5 × 10−3 Ω cm2 at room temperature. Light emission and diode operation at temperatures >750 °C indicated superior stability of the electrical contact. The n-type layer was characterized by SIMS indicating a phosphorus incorporation of ~2 × 1019cm-3 and for the nano-carbon layer a nitrogen incorporation of ~5 × 1020cm−3. Addressing contact limitations to n-type diamond through the growth of moderately phosphorus doped epilayers followed by highly nitrogen doped nano-carbon layers could provide a preferred approach for electronic devices that could also be extended to (100) surfaces.

Original languageEnglish (US)
Article number107607
JournalDiamond and Related Materials
Volume101
DOIs
StatePublished - Jan 2020

Fingerprint

Diamond
Electron emission
Diamonds
Diodes
Carbon
Phosphorus
Nitrogen
Light emission
Plasma enhanced chemical vapor deposition
Electron sources
Electron affinity
Boron
Argon
Epilayers
Metallurgy
Secondary ion mass spectrometry
Power electronics
Excitons
Lithography
Hydrogen

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Chemistry(all)
  • Mechanical Engineering
  • Materials Chemistry
  • Electrical and Electronic Engineering

Cite this

Electrical contact considerations for diamond electron emission diodes. / Koeck, Franz A.; Benipal, Manpuneet; Nemanich, Robert J.

In: Diamond and Related Materials, Vol. 101, 107607, 01.2020.

Research output: Contribution to journalArticle

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