Characteristics of InAlGaAs/InAlAs superlattice avalanche photodiodes for ultra-low optical power detection in the near infrared

Static characteristics of two different structured InAlGaAs/InAlAs superlat tice avalanche photodiodes (SLAPDs) cooled by liquid nitrogen were evaluate d at a wavelength of 1.5 mu m. The dark current of the SLAPD having a thick superlattice layer of 0.504 mu m was 5 x 10(-13) A. This was successively reduced by four orders of magnitude compared to that of the thin layer SLAP D of 0.231 mu m at a breakdown voltage of around 20 V. The thickened layer was effective in suppressing tunneling dark current. An output current of 1 .7 x 10(-12) A at a bias voltage of 15 V was measured for an optical input with a wavelength of 1.5 mu m and a signal power of 1 x 10(-12) W. This sho wed a sharp distinction from the dark current.