High Speed InAlAs/InGaAs Double Heterostructure p-i-n's

MBE grown double heterostructure InAlAs/InGaAs p-i-n photodiodes have been flip-chip mounted on coplanar waveguides. Two methods: (i) incorporation of doping setback InAlAs layers between the InGaAs absorption region and the doped InAlAs layers and (ii) compositional grading have been used to reduce carrier pile-up at the heterointerfaces. Although both methods improve the diode performances, the best results were obtained with compositional grading: a quantum efficiency of ≈38 % at 1.3 μm, a rise time of ≈21 ps and a FWHM of ≈40 ps have been obtained for a device with a 24×24 μm 2 area and a 0.5 μm thick absorption region.