Device Characterization of a Sulfur-Implanted p$^{++}$/p GaSb Photovoltaic Camel Diode

The implantation and rapid thermal annealing of sulfur (S+) ions has previously been shown to be an effective method in non-epitaxially attaining hole carrier concentrations as high as $1\times {10^{19}} \; \rm cm^{-3}$ in gallium antimonide (GaSb). This technique was used to fabricate a photovoltaic diode by delta-doping the front surface of a p-type GaSb substrate and forming a p++/p junction. The steep potential created using this process is increased by strong Fermi level pinning at the metal/p++ interface, resulting in a camel diode with a barrier height of 0.51 eV. A post-fabrication etch process succeeded in improving the short circuit current density to 41.8 mA/cm $^2$ and the internal quantum efficiency to 90% by enhancing the carrier lifetime away from the front metal contact grid. Likewise, the open circuit voltage improved to 0.21 V, with an intrinsic fill factor above 40%. These results offer the potential of a significantly higher power output than similar non-epitaxial devices made on n-type GaSb substrates.