Growth and characterization of InGaAs/GaAsSb type II superlattice absorbers for 2 µm avalanche photodiodes

Avalanche photodiodes (APDs) are critical components for a variety of remote sensing applications, particularly for 3D imaging using light detection and ranging (LiDAR). APDs can provide higher sensitivity and faster response times than traditional PIN diodes due to their internal gain. To apply LiDAR to gas monitoring applications, including greenhouse gases, APDs need to be sensitive further into the infrared than Si APDs can detect. This work investigates an absorber that is sensitive to 2 μm and compatible with an APD. A separate absorption, charge, and multiplication (SACM) heterostructure is often used to reduce the dark current of an infrared APD. In a SACM design, the absorber is placed in a low field region to minimize tunneling and the multiplier is placed in a high field region to maximize impact ionization. We have previously explored high performance multipliers that are lattice matched to InP substrates. In this work, we explore a candidate lattice-matched absorber, an In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 Type II superlattice (T2SL). We have demonstrated photoluminescence at 2 μm using a 5 nm InGaAs/5 nm GaAsSb T2SL structure. We have grown and fabricated 1-micron thick PIN diodes with this absorber material and obtained an n-type background carrier concentration of 5×10¹⁵ cm^-3 . We are currently undertaking the radiometric characterization of these devices to support their integration into a SACM APD.