| Summary: | 碩士 === 國立交通大學 === 電子研究所 === 106 === In this thesis, we fabricated a heterostructure of Ge Quantum Dots/SiO2/SiGe in the channel of a MOSFET in a single oxidation step. Applying the buried oxide layer of SOI substrate and the 2-D tapered Si3N4 waveguide as the cladding and core layer for butt-coupling, respectively. For normal incidence optimal transmission, we chose ITO as the gate electrode. In other words, we demonstrated a waveguided phototransistor which can be measured either by normal incidence or lateral incidence, the absorption layer consists of Ge QDs and SiGe shell . We controlled the gate oxide thickness of 38.5 nm and 3.5 nm by means of dry etching.
In the darkness, good switching behavior (subthreshold swing of 80 mV/decade), and high on/off ratio (Ion/Ioff = 3.41×108 A/A) were measured on the phototransistor with tox=3.5 nm at 300K. At off state, photocurrent gains are 108, 300, and 30 A/A under a normal incidence power of about 1.9 mW at 850 nm, 1310 nm, and 1550 nm, respectively. At on state, photoresponsivities are 139.4, 2.23, 6.81 A/W under a normal incidence power of about 0.1 μW at 850 nm, 1310 nm, and 1550 nm, respectively. Indicating that the phototransistor has a significant photodetection in the near-infrared regime. After the edge polishing, photocurrent gain value of 15.3 A/A under a lateral incidence power of 143 μW at 850 nm are measured on the phototransistor with tox=38.5 nm. The waveguided phototransistor would provide a better access to Si optical interconnect and make the integration more feasible.
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