Design Considerations for 1.3 $\mu$ m GaNAsSb–GaAs High Speed and High Quantum Efficiency Waveguide Photodetectors

The electrical and optical characteristics of a 1.3 mum GaNAsSb-GaAs p-i-n waveguide photodetector (WGPD), consisting of GaAs inner and Al_xGa_1-xAs outer cladding layers, were simulated using a lumped-element model and finite difference beam propagation method (BPM). The effect of multiple cladding layers´ thicknesses and aluminum composition on the quantum efficiency was investigated to provide design guide and deduce the range of parameters needed for achieving quantum efficiency higher than 89%. The simulation shows that a p-i-n waveguide structure with 10 mum length, 4 mum ridge width, 2.4 mum ridge height and 0.4 mum GaN_0.033As_0.887Sb_0.08 core layer thickness can exhibit a theoretical cut-off frequency limit of over 80 GHz. Maximum quantum efficiency of 91.5% can be obtained for this structure with cladding layer thickness of 0.5 mum for GaAs and 0.5 mum for Al _0.7Ga_0.3As.