Designer germanium quantum dot phototransistor for near infrared optical detection and amplification. (15th January 2015)

• Record Type: Journal Article
• Authors: Kuo, M H; Lai, W T; Hsu, T M; Chen, Y C; Chang, C W; Chang, W H; Li, P W
• Is Part Of: Nanotechnology. Volume 26:Number 5(2015)
• Publication Date: 2015-01-15
• Subjects: germanium quantum dots -- MOS phototransistor -- optical interconnect; 73.63.Kv -- 85.35.Be -- 85.60.Bt -- 85.60.Dw; Nanotechnology -- Periodicals; Nanotechnology -- Periodicals; Nanotechnology; Publications périodiques; Nanotechnologies; Periodicals; 620.5
• DOI: 10.1088/0957-4484/26/5/055203
• Languages: English
• ISSNs: 0957-4484

Abstract

Abstract: 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 μ m −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 A W −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.