| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 107 === This paper develops integrated UV sensor and LED warning light. The wafers used are commercial GaN wafers, designed through a mask and utilizing the Silicon Diffusion process. Selectively inverting part of the uppermost layer of p-GaN into n-GaN, and changing its structure from p-i-n to n-p-i-n structure. Three components of light-emitting diode, p-i-n structured photodetector and n-p-i-n structured phototransistor on the same wafer. The characteristics of light-emitting diodes are measured. The characteristics of two different electron blocking layer wafers of n-p-i-n photodetectors included dark current, external quantum efficiency, responsivity under different bias voltages, and responsivity. And then, The operational amplifier is used to convert the photodetector photocurrent signal into a voltage signal and then passes the secondary amplification to reach the LED Turn-on voltage. In this way, invisible UV light can be seen and alerted through visible LED.
First, In the photoelectric characteristics, the turn on voltage of the light-emitting diode is about 3.0 V, and the series resistance is about 159 Ω. The light output power of the light-emitting diode at a current of 10 mA is 4.8 mW. It’s proving that this integrated process is successfully compatible.
Then compare the photodetectors made by QRBAH and FEBI. The external quantum efficiency peak wavelengths are 384 nm and 380 nm, respectively. The external quantum efficiency of QRBAH are 37.2 %, 46.1 %, 54.3 %, 56.2 %, 64.8 %, 88.0 %, 109 % under different reverse bias voltages of 0 V, 1.5 V, 3 V, 5 V, 7 V, 9 V, and 11 V, respectively. The FEBI external quantum efficiency are 30.3 %, 32.2 %, 33.1 %, 39.5 %, and 76.1 % at different reverse bias voltages of 0 V, 1.5 V, 3 V, 5 V, and 7 V, respectively. The two n-p-i-n components have similar photoelectric characteristics, and the current gain starts at 7 V at the reverse bias voltage, and the peak external quantum efficiency and responsivity are similar, but the response speed is different.
The current signal for detecting UV light is converted into a voltage signal using an n-p-i-n component. And the amplified voltage signal is amplified to successfully turn-on the LED. Therefore, the n-p-i-n component is more suitable as an ultraviolet light detector, and the responsivity higher than that of the p-i-n photodetector. Integration with LEDs not only eliminates the cost of special epitaxy, but also adds functionality. For example, LEDs are used as warning lights in this experiment.
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