Impact Ionization Engineering in Antimonide Heterostructures for Avalanche Photodiodes

Development of low noise avalanche photodiodes (APDs) in the short wave infrared (1.5-3 microns) and mid-wave infrared (3-5 microns) requires engineering of the impact ionization process. State of the art APDs are based on based on interband transitions in mercury cadmium telluride (MCT, HgCdTe) with large multiplication gains and low excess noise factors due to the favorable bulk bandstructure that promotes single carrier impact ionization. We have investigated the multiplication characteristics of three different multipliers on InP substrate (AlGaInAs (M1), AlGaAsSb (M2) and AlInAsSb (M3)). We have demonstrated decrease in the excess noise factors using ternary superlattices and extremely low excess noise factors (k~0.01) and low dark current density (~10 μA/cm² ) at 300K. We will discuss the research challenges associated with the design, growth, fabrication and radiometric characterization of these APDs and the potential for the development of these critical APD components for LiDAR and active remote sensing and imaging systems.