| dc.description.abstract | Single-photon avalanche diode (SPAD) is widely used in medical electronics, optical fiber communication, automatic driving systems, etc. In the past, InGaAs was mainly used as the absorption layer and InP was used as the multiplication layer material. However, using InAlAs as a multiplication layer has a higher avalanche probability, and it is expected to have a higher photon detection efficiency. In addition, InAlAs is less sensitive to temperature, so the operating temperature is more flexible; Furthermore, in order to further improve the photon detection efficiency, we incorporate a distributed Bragg reflector at the bottom of the N contact layer, and the high reflection of the distributed Bragg reflector is applied to prolong the stay of the incident photon in the device, so that the absorption probability can be improved, thereby improving the photon detection efficiency. Therefore, this study adopts InAlAs as multiplication layer and incorporates the distributed Bragg reflector structure for further investigation.
The device was processed into mesa type, which relies on the etching to define the active detection size of the device. Sulfur treatment is performed on the exposed side wall and following a passivation layer is applied to reduce the leakage current of the device. The last we deposited the cathode and anode of the device. The chip was wire bonded to the circuit board to perform the subsequent measurements. By operating the SPAD under different excess bias voltage, operating frequency and temperature, we can comprehensively characterize the SPAD and thoroughly study the physics behind.
The breakdown voltage of the device at room temperature is 32.7 volts, the temperature coefficient is 10 mV/K; Under the operating conditions of pulse width of 5 ns, temperature of 187.5 K, and excessive bias of 4.0 %, the single photon detection efficiency reaches 1.7%, dark count probability was 9.6%. By using the illuminated double-gate method, the probability of afterpulsing is less than 1 % under the repetition rate of 20 kHz. The timing jitter is reduced to 59ps when the excessive bias increases to 5.5%. | en_US |