| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 104 === In this thesis, we investigate two characteristics of (1) the temperature-sensing effect and (2) the optical-to-electrical signal transmission in light-emitting transistors (LETs). By embedding the quantum well (QW) into the base region of the heterojunction bipolar transistor (HBTs), the HBTs will form the QW-HBTs (or so-called LETs). In the temperature-sensing investigation, we analyze the thermal effects on the electrical signals. Comparing the temperature-dependent current gain, β(T), in QW-HBTs to the current gain of the normal HBTs, we can observe the totally opposite trend, presenting that the QW plays an important role in the thermal mechanism. We derive the modified charge control model and rate equations to analyze the carrier capturing and escaping behavior related to the QW and the carriers coupling to the whole base charge. Moreover, we alter the epitaxial structures and compare the effects on the trend of β(T) through the theoretical model we build and simulation software. We can find out the optimal layer design of current gain curve for applying to the temperature sensing in the future. For the effects on the different device geometries, because of many non-ideal effects, we directly fabricate the QW-HBT devices with different layout designs and variations. Also the simulation tool is used to help the analyses of the thermal effects on the β(T).
In the optical-to-electrical signal transmission part, we demonstrate the integration of optoelectronic system realized by the ring-shaped light-emitting transistors, or RLETs. We fabricate the LETs with the ring-shaped resonator structures, and analyze the effects of different sizes and geometries on the optical and electrical outputs. Owing to the whispering gallery modes (WGMs), the optical modes will propagate along the ring periphery without any output direction. In order to communicate to other devices, we incorporate the waveguides to guide the light in the specific direction. In the end of the waveguide, we incorporate the photodetectors which consist of the same epitaxial structure of RLETs. According to Franz-Keldysh effect, the light from the RLETs can be transferred to the electrical signal by the base-collector junction of the detector LETs, and hence we can calculate the responsivity. This thesis presents the functional characteristics of LETs, and we hope to contribute to the development of the optoelectronic integrated circuits (OEICs) in the future.
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