High-performance near-IR photodiodes: A novel chemistry-based approach to Ge and Ge-Sn devices integrated on silicon

Radek Roucka, Jay Mathews, Change Weng, Richard Beeler, John Tolle, Jose Menendez, John Kouvetakis

Research output: Contribution to journalArticlepeer-review

84 Scopus citations


Ge/Si heterostructure diodes based on n++Si(100)/i-Ge/p-Ge and p++Si(100)/i-Ge/n-Ge stacks and intrinsic region thickness of ∼350 and ∼ 900 nm, respectively, were fabricated using a specially developed synthesis protocol that allows unprecedented control of film microstructure, morphology, and purity at complementary metal-oxide- semiconductor compatible conditions. From a growth and doping perspective, a main advantage of our inherently low-temperature (390 °C) soft-chemistry approach is that all high-energy processing steps are circumvented. Current-voltage measurements of circular mesas (60-250 μm in diameter) show dark current densities as low as 6 × 10-3 A/cm2 at -1 V bias, which is clearly improved over devices fabricated under low thermal budgets using traditional Ge deposition techniques. Spectral photocurrent measurements indicate external quantum efficiencies between 30 and 60% of the maximum theoretical value at zero bias, and approaching full collection efficiency at high reverse biases. The above Ge devices are compared to analogous low-temperature-grown (350 ° C) Ge0.98Sn0.02 diodes. The latter display much higher dark currents but also higher collection efficiencies close to 70% at zero bias. Moreover, the quantum efficiency of these Ge0.98Sn0.02 diodes remains strong at wavelengths longer than 1550 nm out to 1750 nm due to the reduced band gap of the alloy relative to Ge.

Original languageEnglish (US)
Article number5689404
Pages (from-to)213-222
Number of pages10
JournalIEEE Journal of Quantum Electronics
Issue number2
StatePublished - 2011


  • Germanium-tin alloys
  • infrared detectors
  • integrated optoelectronics
  • p-i-n
  • photodiodes
  • photovoltaic cell materials
  • semiconductor epitaxial materials
  • ultrahigh vacuum chemical vapor deposition

ASJC Scopus subject areas

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


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