Interdigitated Ge p-i-n photodetectors fabricated on a Si substrate using graded SiGe buffer layers

Jungwoo Oh, Joe C. Campbell, Shawn G. Thomas, Sushil Bharatan, Rainer Thoma, Craig Jasper, Robert E. Jones, Tom E. Zirkle

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We report an interdigitated p-i-n photodetector fabricated on a 1-μm-thick Ge epitaxial layer grown on a Si substrate using a 10-μm-thick graded SiGe buffer layer. A growth rate of 45 Å/s∼60 Å/s was achieved using low-energy plasma enhanced chemical vapor deposition. The Ge epitaxial layer had a threading dislocation density of 105 cm-2 and a rms surface roughness of 3.28 nm. The 3-dB bandwidth and the external quantum efficiency were measured on a photodetector having 1-μm finger width and 2-μm spacing the a 25 × 28 μm2 active area. At a wavelength of 1.3 μm, the bandwidth was 2.2, 3.5, and 3.8 GHz at bias voltages of -1, -3, and -5 V, respectively. The dark current was 3.2 and 5.0 μA at -3 and -5V, respectively. This photodetector exhibited an external quantum efficiency of 49% at a wavelength of 1.3 μm.

Original languageEnglish
Pages (from-to)1238-1241
Number of pages4
JournalIEEE Journal of Quantum Electronics
Issue number9
Publication statusPublished - 2002 Sept

Bibliographical note

Funding Information:
Manuscript received March 5, 2002; revised May 14, 2002. This work was supported by the Motorola SABA program and the Semiconductor Research Corporation. J. Oh and J. C. Campbell are with the University of Texas at Austin, Austin, TX 78712 USA (e-mail: S. G. Thomas and C. Jasper are with Motorola, DigitalDNA Laboratories, Mesa, AZ 85202 USA. S. Bharatan, R. Thoma, and T. E. Zirkle are with Motorola, DigitalDNA Laboratories, Tempe, AZ 85284 USA. R. E. Jones is with Motorola, DigitalDNA Laboratories, Austin, TX 78721 USA. Publisher Item Identifier 10.1109/JQE.2002.802165.

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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