Low-noise InGaAs APD Based on Micro-Scaled Photonic Structures for Low Light Imaging Application

In this work, we designed an InGaAs APD with a higher photocurrent to dark current ratio than a regular APD. The improvement is based on optical confinement in an optical resonator, which is able to increase the optical intensity in the detector volume and thus its quantum efficiency. With optical confinement, the absorbing layer can be 20 times thinner than the regular APD, reducing the dark current by the same amount and still be able to produce 90.9% of the photocurrent. The I-p/I-d ratio can thus be increased by 18.2 times in concomitant with a lower operating voltage. Higher photocurrent can also be obtained using a thicker absorber. To further increase the detection sensitivity, we designed an efficient InGaAsP LED having the similar resonator geometry. The resonator geometry enables more collimated emission and increases the optical power theoretically by more than 36 times compared with a regular LED. Integrating the resonant APD and LED together will yield a powerful SWIR transceiver for various low light, LIDAR, and 3-dimensional imaging applications.