Optical response time of InGaAs(P)/InP photodiodes

Speed of response of InGaAs(P)/InP based photodiodes has been analysed with structure parameters and as a function of bias voltage. It is shown that there exists a strong dependence of response time on the valence band discontinuities at the heterointerface InGaAs(P)/InP in the SAM photodiode structure (pile-up effect). The graded InGaAsP layer between absorption layer InGaAsP and InP multiplication layer in photodiode structure can successfully reduce this effect. The best measured InGaAs(P)/InP photodiodes have rise time and fall time at bias voltage 5-10 V better than 400 ps.