Low-Noise Analog APDs with Impact Ionization Engineering and Negative Feedback

Future NASA LIDAR missions require low noise and large area photodetectors operated at short-wave infrared (SWIR) wavelengths. Silicon avalanche photodiodes have very low responsivity for wavelength longer than 1.1 um; and while InP-based APDs have high responsivity in the SWIR region, they exhibit high noise equivalent powers (NEPs) due to the relatively high excess noise of bulk InP multiplication regions. We propose to develop low-noise analog APDs operating in the SWIR region by incorporating impact ionization engineered structures coupled with an epitaxial negative feedback gain quenching mechanism into the multiplication region of linear mode APDs. The goal is to develop large-area (>250 um diameter), low-noise SWIR detectors with high quantum efficiency (>75%), high bandwidth (~100 MHz), and very low NEP approaching NASA targets of 20 fW/rt(Hz). In addition to discrete device characterization, these devices will be incorporated into prototype LIDAR receivers for performance assessment.