Material defects are one of the keys limiting factors for semiconductor device performances and reliability. In this work, the impact of surface bump defects in 4H-SiC epi-material on the performance of Avalanche Photodiodes (APDs) are investigated for ultraviolet (UV) detection. Based on the 4H-SiC epi-material with a concentration of ~104 cm-2 for surface bump defects, 4H-SiC APDs were fabricated and characterized. The results demonstrate that surface bump defects have no effect with the leakage current of devices at low reverse voltage. However, premature breakdown or even device failure will be caused due to the surface bump defects. It is proved that surface bump defects can be ignored for low-voltage photodiodes but must be taken into account for APDs. The physical mechanism and suppression of surface bump defects in 4H-SiC epi-material are further analyzed. Optimization of C/Si ratio for source gas during the growth process of epilayer will help to suppress the formation of surface bump defects. This work will be useful for researchers in the related fields of 4H-SiC photodiode UV detectors.
In this work, 4H-SiC avalanche photodiodes (APDs) were fabricated and investigated both in linear and Geiger modes for high-temperature ultraviolet (UV) detection applications. With the temperature varying from 300 K to 425 K, the avalanche breakdown voltage of our 4H-SiC APDs keeps very stable with a small temperature coefficient of <8 mV/K. In the Geiger mode, the impact of temperature on the output signal pulse height, dark count rate (DCR) and single-photon-detection efficiency (SPDE) is analyzed from the aspect of device physics. At a fixed bias voltage of 166.5 V, the DCR and SPDE at 300 K, 375 K and 425 K are 5.3 Hz∙μm-2 /15.6%, 11.8 Hz∙μm-2 /17% and 16.5 Hz∙μm-2 /15.7%, respectively. The results in this work demonstrate that our fabricated 4H-SiC APDs can operate stably and reliably under the conditions with a high temperature.
In this letter, an avalanche photodiode (APD) for ultraviolet detection was fabricated on a 4H-SiC epi-layer with a radius of 150 µm. By adopting passive quenching method, the impact of quenching resistor on single photon detection performance of the fabricated APD was investigated for the first time. It is found that both dark count rate (DCR) and single photon detect efficiency (SPDE) were reduced with the increasing quenching resistance. When the DCR fixed at 5 Hz/μm2 , the SPDE is 7.1% /6.7%/5.4%/5.2% corresponding to the quenching resistance of 10/20/50/100 kΩ. Variation of the SPDEs can be ascribed to the changing death time by comparing the photon counting spectra with various resistors. The obtained results have built up a good basis for the design of SiC APD single photon detection.
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