Influence of lattice constants of GaN and InGaN on npn-Type GaN/InGaN heterojunction bipolar transistors

Toshiki Makimoto, Takatoshi Kido, Kazuhide Kumakura, Yoshitaka Taniyasu, Makoto Kasu, Nobuo Matsumoto

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We investigated the a- and c-axis lattice constants of GaN buffer and 180-nm-thick p-InGaN layers grown on SiC and sapphire substrates using reciprocal space mapping of the X-ray diffraction intensity. It was found that the a-axis lattice constant of the GaN buffer layer on a SiC substrate is larger than those of unstrained GaN and a GaN buffer layer on a sapphire substrate. As a result, the p-InGaN layer on GaN/SiC is fully strained even at the In mole fraction of 9.0% where that on GaN/sapphire is relaxed. This result means that fewer defects are generated in p-InGaN on GaN/SiC at higher In mole fractions. This is another advantage of SiC substrate for npn-type GaN/InGaN heterojunction bipolar transistors, in addition to its high thermal conductivity. The collector current density dependence of current gain shows the ideality factor of 2 for GaN/InGaN HBTs on both SiC and sapphire substrates. This is ascribed to the recombination current at the emitter-base interface, which arises from the threading dislocations generated at the interface between the substrate and nitride buffer layer.

Original languageEnglish
Pages (from-to)3395-3397
Number of pages3
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume45
Issue number4 B
DOIs
Publication statusPublished - 2006 Apr 25
Externally publishedYes

Fingerprint

Heterojunction bipolar transistors
bipolar transistors
Lattice constants
heterojunctions
Sapphire
sapphire
Substrates
Buffer layers
buffers
Nitrides
accumulators
nitrides
Thermal conductivity
emitters
Current density
thermal conductivity
current density
X ray diffraction
Defects
defects

Keywords

  • GaN
  • HBT
  • Lattice constant
  • MOVPE
  • P-InGaN
  • Sapphire
  • SIC
  • Strain

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Influence of lattice constants of GaN and InGaN on npn-Type GaN/InGaN heterojunction bipolar transistors. / Makimoto, Toshiki; Kido, Takatoshi; Kumakura, Kazuhide; Taniyasu, Yoshitaka; Kasu, Makoto; Matsumoto, Nobuo.

In: Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Vol. 45, No. 4 B, 25.04.2006, p. 3395-3397.

Research output: Contribution to journalArticle

Makimoto, Toshiki ; Kido, Takatoshi ; Kumakura, Kazuhide ; Taniyasu, Yoshitaka ; Kasu, Makoto ; Matsumoto, Nobuo. / Influence of lattice constants of GaN and InGaN on npn-Type GaN/InGaN heterojunction bipolar transistors. In: Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers. 2006 ; Vol. 45, No. 4 B. pp. 3395-3397.
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AU - Matsumoto, Nobuo

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AB - We investigated the a- and c-axis lattice constants of GaN buffer and 180-nm-thick p-InGaN layers grown on SiC and sapphire substrates using reciprocal space mapping of the X-ray diffraction intensity. It was found that the a-axis lattice constant of the GaN buffer layer on a SiC substrate is larger than those of unstrained GaN and a GaN buffer layer on a sapphire substrate. As a result, the p-InGaN layer on GaN/SiC is fully strained even at the In mole fraction of 9.0% where that on GaN/sapphire is relaxed. This result means that fewer defects are generated in p-InGaN on GaN/SiC at higher In mole fractions. This is another advantage of SiC substrate for npn-type GaN/InGaN heterojunction bipolar transistors, in addition to its high thermal conductivity. The collector current density dependence of current gain shows the ideality factor of 2 for GaN/InGaN HBTs on both SiC and sapphire substrates. This is ascribed to the recombination current at the emitter-base interface, which arises from the threading dislocations generated at the interface between the substrate and nitride buffer layer.

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