Photocurrent multiplication in ion implanted lateral In/sub 0.2/Ga/sub 0.8/As/GaAs strained-layer superlattice photodetectors

We demonstrate the first Be+-implanted lateral In/sub 0.2/Ga/sub 0.8/As/GaAs strained-layer superlattice (SLS) avalanche photodetector. This planar device exhibits low capacitance (<1 pF), low dark current (less than 6 nA at -60 V), and large active area (100 μm x 250 μm at -50 V). In addition, an uncoated external quantum efficiency of 50% at -50 V between 775 and 880 nm is observed with response continuing to 1.03 μm. Detailed photocurrent measurements confirm the occurrence of photocurrent multiplication and indicate that the ionization coefficient of electrons is larger than that of holes for transport in the plane of the SLS. This work demonstrates the advantages of exploiting the preferred transport direction that occurs in superlattice structures through the use of ion implantation