Browsing by Author "Kuo, M. H."

Now showing 1 - 4 of 4

Counter-intuitive Ge/Si/O interactions and Ge/Si symbiosis enable the creatation of new classes of exciting nanoelectronic and nanophotonic devices
(2017-01-01)
Hsueh, C. Y.
;
Huang, T. L.
;
Peng, K. P.
;
Kuo, M. H.
;
Lin, H. C.
We have successfully exploited multi-dimensional spaces of concentrations of the interstitial species, Si and Ge, geometries and compositions of the starting SiGe nano-pillar, and sources of Si interstitials (the Si3N4 and Si encapsulation layers) to create new classes of exciting optical and electronic devices such as single-electron tunneling devices, wavelength tunable photodetectors, and MOSFETs.
Designer germanium quantum dot phototransistor for near infrared optical detection and amplification
(2015-02-06)
Kuo, M. H.
;
Lai, W. T.
;
Hsu, T. M.
;
Chen, Y. C.
;
Chang, C. W.
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 similar to 0.27 pA mu m(-2)), a high on-off current ratio (I-on/I-off similar to 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 x 10(6) and 1.7 AW(-1), respectively, under an incident power of 0.9mW 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.
"Embedded Emitters": Direct bandgap Ge nanodots within SiO2
(2016-12-21)
Kuo, M. H.
;
Chou, S. K.
;
Pan, Y. W.
;
Lin, S. D.
;
George, T.
Microdisk-arrays of vertically stacked 30-70nm Ge nanodots embedded within SiO2 were fabricated using thermal oxidation of Si0.75Ge0.25 abacus-shaped pillars and followed by post-annealing in oxygen-deficient conditions. The Ge nanodots are subjected to increasing quantum-confinement and tensile-strain by reducing dot size. We show that considerable quantum-confinement and tensile-strain can be generated within 30 nm Ge nanodots embedded in SiO2, as evidenced by large Raman red shifts for the Ge-Ge phonon lines in comparison to that for bulk Ge. These large quantum-confinement and tensile-strain facilitate direct-bandgap photoluminescence experimentally observed for the Ge nanodots, and are consistent with the strain-split photoluminescence transitions to the light-hole (LH) and heavy-hole (HH) valence bands at 0.83 eV and 0.88 eV, respectively. Time-resolved photoluminescence measurements conducted from 10-100K show temperature-insensitive carrier lifetimes of 2.7 ns and 5 ns for the HH and LH valence-band transitions, respectively, providing additional strong evidence of direct bandgap photoluminescence for tensile-strained Ge nanodots. Published by AIP Publishing.
Self-organized gate stack of Ge nanosphere/SiO2/Si1-xGex enables Ge-based monolithically-integrated electronics and photonics on Si platform
(2018-01-01)
Liao, P. H.
;
Kuo, M. H.
;
Tien, C. W.
;
Chang, Y. L.
;
Hong, P. Y.
We report the first-of-its-kind, self-organized gate stack of Ge nanosphere (NP) gate/SiO2/Si1-xGex channel fabricated in a single oxidation step. Process-controlled tunability of the Ge NP size (5-90nm), SiO2 thickness (2-4nm), and Ge content (x = 0.65-0.85) and strain engineering (epsilon(comp) = 1-3%) of the Si1-xGex are achieved. We demonstrated Ge junctionless (JL) n-FETs and photoMOSFETs (PTs) as amplifier and photodetector, respectively, for Ge receivers. L-G of 75nm JL n-FETs feature I-ON/I-OFF > 5x10(8), I-ON > 500 mu A/mu m at V-DS = 1V, T= 80K. Ge-PTs exhibit superior photoresponsivity > 1,000A/W and current gain linearity ranging from nW-mW for 850nm illumination. Size-tunable photo-luminescence (PL) of 300-1600nm (NUV-NIR) are observed on 5-100nm Ge NPs. Our gate stack of Ge NP/SiO2/Si1-xGex enables a practically achievable building block for monolithically-integrated Ge electronic and photonic ICs (EPICs) on Si.