applied to the fabricated chip the breakdown voltage vb was 30 v and the dark current at 0 9 vb was 100 na both sufficiently low in a high temperature reverse biased test to predict reliability it was found that a high level of reliability corresponding to 100 000 hours at 85 u00b0 c was achieved fig1 is a sectional view for describing a back illuminated type avalanche photo diode which is fabricated according to the present invention a method for its fabrication will be described with reference to fig1 a 15 b 15 c 15 d and 15 e fig1 a is a sectional view of a semiconductor layer that was used wherein reference numeral 201 denotes an inp substrate n type 2 u00d7 10 18 cm u2212 3 202 an inalas buffer layer n type 2 u00d7 10 18 cm u2212 3 0 7 u03bcm 203 an inalas multiplication layer n type 5 u00d7 10 14 cm u2212 3 0 2 u03bcm 232 an inalas field control layer p type 7 u00d7 10 17 cm u2212 3 0 02 u03bcm 233 an ingaas field control layer p type 7 u00d7 10 17 cm u2212 3 0 01 u03bcm 234 an inalas field control layer p type 7 u00d7 10.