Fabrication of InAs/GaSb type-II superlattice LWIR planar photodiodes

Abstract

We have evaluated selective doping techniques for the fabrication of type II LWIR superlattice planar detectors. Ion-implantation and diffusion of dopants were evaluated for selective doping of the electrical junction region in planar photodiodes. Residual damage remains when superlattice structures are implanted with Te ions with an energy of 190 keV and a dose of 5x1013 cm-2, at room temperature. Controlled Zn diffusion profiles with concentrations from 5x1016 to > 5x1018 cm-3 in the wide bandgap cap layer was achieved through a vapor phase diffusion technique. Planar p-on-n diodes were fabricated using selective Zn diffusion. The I-V characteristics were leaky due to G-R and tunneling in the homojunction devices, for which no attempts were made to optimize the n-type absorber doping level. Work is underway for the implementation of planar diodes with the n-on-p architecture through selective Te diffusion. Due to increased minority carrier lifetimes for p-type InAs/GaSb superlattice absorber layers, planar device with the n-on-p architecture have the potential to provide improved performance as compared to the p-on-n counterparts.