| 摘要 |
PURPOSE:To form an avalanche photodiode (APD) which exhibits preferable frequency characteristics with low amplification factor by setting the density of a pi layer of an active region of a hyper abrupt junction structure to a specific value, ion implanting the dosage of a P type layer in a specific value, and setting the width of the P type layer to the specific value, thereby decreasing the amplification factor MRT of reach-through to the vicinity of 1. CONSTITUTION:An Si-APD is selected in impurity density of a P<-> type epitaxial layer to 1X10<14>cm<-3> to 5X10<14>cm<-3> with a P<+> type substrate 1 as a pi layer 2, thereby forming an oxidized film 3 of 1,000Angstrom thick. Then, a resist 4 is coated through a mask, a window 5 is opened at the light absorbing layer part of the APD part, and boron ions are implanted by ion implantation to the layer to form a P type layer 6. The accelerating voltage of the B<+> ions at this time is 300keV and the implantation amount of 2.13X10<12>cm<-2>, and this value is actually preferred in the range of 2-5X10<12>cm<-2>. Then, it is heat treated at 1,200 deg.C. The time at this time relates to the amplification factor and the excess noise coefficient. The implanted boron is doped in the pi layer in response to the gauss distribution. The width of the P type layer at this time is preferably 7-9mum. An oxidized film 3a is formed on the P type layer at this time. |
