The authors propose two novel designs of a waveguide photodiode for ac
cess networks; one is a planar waveguide conjunction with impurity dif
fusion to simplify the fabrication process and the other is an intenti
onally p-type doped photoabsoption layer to lower the operating voltag
e. Without degrading the efficiency, the fabricated device has a bandw
idth of 500 MHz at 1 V and 250 MHz even at 0 V.