PHOTONCOUNTING IN INFRA-RED REGION WITH SUPERLATTICE AVALANCHE PHOTODIODES

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The purpose of this research is to investigate the characteristic performance of an InAlGaAs/InAlAs superlattice avalanche photodiode (SLAPD) as an ultra-low light detecting device for photoncounting method in infra-red region. The results are mainly summarized as follows.1) The SLAPD's were cooled by a liquid-nitrogen cooling system and operated at 85 K.2) As the decrease of the dark current noise of the thin-layr SLAPD was remarkably seen in the low bias voltage condition, the main component of the noise was caused from the thermally excited carriers. The breakdown voltage of the SLAPD moved to lower one by the cooling. 3) Dark current noise of the thick-layr SLAPD was successively reduced to 10-11 A at around the breakdown voltage, on the other hand that of the thin-layr SLAPD was 10-9 A.The noise was supposed the tunneling dark current. It was shown that the superlattice multiplication layr was effective to control the excess noise coefficient and the thickened layr was also effective to suppress the tunneling dark current. This SLAPD could be used in optical power of 10-6 W to 10-12 W.4)Photoncounting by using the thick-layr SLAPD was tried, but the pulse height distribution of the signal did not show a clear difference between the light signal pulse and the noise pulse. The dark current noise caused from the microplasma was still left.These results shows that the SLAPDs with the thicker superlattice layr have a potential for the photoncounting device in infra-red region. The development of the design and fabrication technique for such devices is strongly requested.