Large area, low capacitance InGaAs PINs

InGaAs PIN detectors are extensively used for detection of photons in the wavelength range between 1000 nm and 1600 nm. Epitaxial InGaAs layers are commonly grown by MOCVD on InP substrates and layers of only a few micrometers are needed to fully absorb all IR radiation. In many applications, large area single- or multi-element InGaAs detectors are required with diameters ranging from 1 mm up to 5 mm. While useful for tracking large spots of IR light, their thin active layers have the disadvantage of a relatively large capacitance, which causes higher noise and reduced bandwidth. A PIN structure was designed with the purpose to reduce said capacitance by half and thus effectively double the value of the bandwidth when compared to standard values of catalog devices. The growth structure will be detailed, electro-optical measurement results will be presented and the next steps for specific markets such as laser spot tracking, semi-active laser guided precision-guided munitions or laser beam alignment over long distances will be presented. The new diodes have half the capacitance of regular PIN photodetectors leading to twice as much bandwidth at a low operating voltage. The combination of controlled epitaxial growth parameters with low defect density and low intrinsic doping in material have yielded new devices with proven reliability at high temperatures. Finally, it will be demonstrated that the change to the structure did not impact other parameters of the photodiode like dark current, breakdown voltage, responsivity or series resistance.