Designer germanium quantum dot phototransistor for near infrared optical detection and amplification

M. H. Kuo, W. T. Lai, T. M. Hsu, Y. C. Chen, C. W. Chang, Wen-Hao Chang, Pei-Wen Li

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We demonstrated a unique CMOS approach for the production of a high-performance germanium (Ge) quantum dot (QD) metal-oxide-semiconductor phototransistor. In the darkness, low off-state leakage (I off ∼ 0.27 pA μm -2 ), a high on-off current ratio (I on /I off ∼ 10 6 ), and good switching behaviors (subthreshold swing of 175 mV/dec) were measured on our Ge-QD phototransistor at 300 K, indicating good hetero-interfacial quality of the Ge-on-Si. Illumination makes a significant enhancement in the drain current of Ge QD phototransistors when biased at both the on- and off-states, which is a great benefit from Ge QD-mediated photoconductive and photovoltaic effects. The measured photocurrent-to-dark-current ratio (I photo /I dark ) and the photoresponsivities from the Ge QD phototransistor are as high as 4.1 × 10 6 and 1.7 AW -1 , respectively, under an incident power of 0.9 mW at 850 nm illumination. A superior external quantum efficiency of 240% and a very fast temporal response time of 1.4 ns suggest that our Ge QD MOS phototransistor offers great promise as optical switches and transducers for Si-based optical interconnects.

Original languageEnglish
Article number055203
Pages (from-to)1-9
Number of pages9
Issue number5
StatePublished - 6 Feb 2015


  • Germanium quantum dots
  • MOS phototransistor
  • Optical interconnect

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