Characteristics of Temperature Effect on Optical Bandwidth and Cut-off Frequency in the Light Emitting Transistors
Date Issued
2015
Date
2015
Author(s)
Lee, I-Te
Abstract
This thesis presents the effects of temperature on the light-emitting transistor (LET), specifically its effects on the DC I-V characteristics and the RF characteristics. The electrical and optical characteristics of the InGaP/GaAs LET with two undoped InGaAs quantum-wells (QWs) embedded in the base region operated from 25℃ to 55℃ are demonstrated. The LET is a unique semiconductor optoelectronic device with both electrical and optical outputs, which provides potential applications in future optical interconnects and photonic integrated circuits. LETs and transistors lasers (TLs) have gotten a lot of attention due to their high-speed characteristics and potential for use in the next era of Internet of Things (IoT). At elevated temperatures, the current gain of the LET is increased and the optical modulation bandwidth is also enhanced. Both findings are interesting and contradictory to the behaviors of conventional heterojunction bipolar transistors (HBTs) or light-emitting diodes (LEDs). The physics of temperature-induced carrier dynamics in the active region of LETs is unique and resulted from the inherent transistor tilted-charge population instead of stored-charge population of diodes. The effective base transit time will decrease with temperature due to the reduction of thermionic emission lifetime. As a result, the cut-off frequency of the LET increases with the temperature which is also different from the conventional HBTs. The thermionic emission in the quantum well increases with temperature resulting in the increase of the current gain. In order to increase the temperature-to-voltage signal for high resolution temperature sensor, the simple circuits are designed and fabricated. Due to the characteristic that the thermionic emission is sensitive to the temperature, it has the potential as the front end of the high resolution smart temperature sensor.
Subjects
light-emitting transistors
current gain
optical bandwidth
cut-off frequency
temperature sensor
Type
thesis
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