Demonstration of high-speed staggered lineup GaAsSb-InP unitraveling carrier photodiodes

We demonstrate staggered ("type-II") lineup lattice-matched GaAs/sub 0.51/Sb/sub 0.49/-InP unitraveling carrier photodiodes (UTC-PDs) for application near 1.55 μm. The GaAsSb absorbing layer conduction band edge lines up /spl Delta/E/sub C/=0.11 eV above that of InP, and hence, allows the direct injection of photogenerated electrons into an InP collector-without any need for compositional grading around the GaAsSb-InP interface-thus simplifying epitaxial growth and device fabrication. InP-GaAsSb UTC-PDs show low dark current levels, and measurable bandwidths are limited by the test equipment. A transit-limited bandwidth of 105 GHz for a PD with a 1000-GaAsSb absorption layer (C:5×10/sup 18//cm
³
) and a 2000 InP collector is inferred from the variation of photoresponse bandwidth with device area.