Avalanche photodetectors and image sensors including the same

An image sensor, comprising:

• a substrate;
• an insulating layer on the substrate;
• a first electrode on the insulating layer;
• a first photodetector on the first electrode;
• and
• a second photodetector on the first photodetector,
• wherein each photodetector of the first photodetector and the second photodetector includes
• a collector layer,
• a tunnel barrier layer on the collector layer,
• a graphene layer on the tunnel barrier layer,
• an emitter layer on the graphene layer, and
• a second electrode on the emitter layer.

An image sensor, comprising:

• a substrate;
• an insulating layer on the substrate;
• and
• a first photodetector and a second photodetector separately on the insulating layer and aligned with each other in a direction that is parallel to a top surface of the insulating layer,
• wherein each photodetector of the first and second photodetectors includes
• a first electrode on the insulating layer,
• a collector layer on the first electrode,
• a tunnel barrier layer on the collector layer,
• a graphene layer on the tunnel barrier layer,
• an emitter layer on the graphene layer, and
• a second electrode on the emitter layer.

An image sensor, comprising:

• a substrate;
• an insulating layer on the substrate;
• and
• a first photodetector and a second photodetector on the insulating layer, at least one photodetector of the first and second photodetectors including
• a first electrode on the insulating layer,
• a collector layer on the first electrode,
• a tunnel barrier layer on the collector layer,
• a graphene layer on the tunnel barrier layer,
• an emitter layer on the graphene layer, and
• a second electrode on the emitter layer.

A light detection and ranging (LiDAR) system, comprising:

• a wavelength-tunable laser diode (LD) configured to emit a light beam;
• an optical phased array (OPA) configured to receive the emitted light beam as an input optical signal and output an optical signal into an environment based on receiving the input optical signal from the LD;
• a receiver configured to receive an optical signal output from the OPA and reflected from an object;
• and
• a controller configured to control the wavelength-tunable LD, the OPA, and the receiver,
• wherein the receiver includes at least one photodetector, the at least one photodetector including
• a first electrode,
• a collector layer on the first electrode,
• a tunnel barrier layer on the collector layer,
• a graphene layer on the tunnel barrier layer,
• an emitter layer on the graphene layer, and
• a second electrode on the emitter layer.