InAlAs/InGaAs metamorphic high electron mobility transistor with Cu/Pt/Ti gate and Cu airbridges

Chun Wei Chang*, Po Chou Chen, Huang Ming Lee, Szu Hung Chen, Kartik Chandra Sahoo, Edward Yi Chang, Muh Wang Liang, Tsung-Eong Hsien

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The use of a Cu/Pt/Ti Schottky contact structure and Cu-based airbridges for high-frequency metamorphic high electron mobility transistor (MHEMT) is successfully developed. The material characteristics of the Cu/Pt/Ti Schottky contact on i-InAlAs were studied. Judging from the results of the X-ray diffraction analysis, Auger electron spectroscopy, and transmission electron microscopy, the Cu/Pt/Ti Schottky contact structure on InAlAs was very stable after annealing at 350°C. However, after 400°C annealing, the reaction of copper with the layers underneath started to occur and formed the Cu 4Ti phase. The Cu-metallized MHEMT using the proposed Cu/Pt/Ti T-gate structure and Cu-based airbridges has a saturated drain current of 673 mA/mm and a maximum transconductance of 750 mS/mm. The gate to drain breakdown voltage measured was 14.5 V at a gate reverse current of -1 mA/mm. The device also demonstrated a cutoff frequency Ft of 90 GHz and a maximum frequency of oscillation Fmax of 165 GHz. An MHEMT with a Au/Pt/Ti gate was fabricated and compared with an MHEMT fabricated with the proposed Cu/Pt/Ti gate. These two kinds of MHEMTs showed similar Ft and F max. These results demonstrate that the Cu/Pt/Ti T-gate and Cu-based airbridges can be used for MHEMT fabrication with excellent electrical characteristics.

Original languageEnglish
Pages (from-to)2848-2851
Number of pages4
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number5 A
StatePublished - 8 May 2007


  • Copper airbridge
  • Copper metallization
  • InAlAs

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