Controlling detection time in photodetectors

Patent metadata

Field	Value
Publication number	US-10971645-B2
Application number	US-201916656891-A
Country	US
Kind code	B2
Filing date	Oct 18, 2019
Priority date	Jan 29, 2018
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

Example embodiments relate to controlling detection time in photodetectors. An example embodiment includes a device. The device includes a substrate. The device also includes a photodetector coupled to the substrate. The photodetector is arranged to detect light emitted from a light source that irradiates a top surface of the device. A depth of the substrate is at most 100 times a diffusion length of a minority carrier within the substrate so as to mitigate dark current arising from minority carriers photoexcited in the substrate based on the light emitted from the light source.

First claim

What is claimed is:

1. A method comprising:
providing a device comprising:
a light source comprising a laser;
a substrate; and
a photodetector coupled to the substrate,
wherein the photodetector is arranged to detect a light signal emitted from the light source upon the light signal being reflected from one or more objects in an external environment and irradiating a top surface of the device;

emitting the light signal from the light source; and
mitigating dark current arising from minority carriers photoexcited in the substrate based on the light signal emitted from the light source.

2. The method of claim 1 , wherein mitigating the dark current comprises emitting the light signal from the light source such that the light signal from the light source irradiates a bottom surface of the device.

3. The method of claim 1 , wherein mitigating the dark current comprises modifying an operating temperature of the device.

4. The method of claim 1 , wherein mitigating the dark current comprises modulating a wavelength of the light signal emitted from the light source.

5. The method of claim 1 , wherein mitigating the dark current comprises modulating a power of the light signal emitted from the light source.

6. The method of claim 1 , wherein mitigating the dark current comprises modulating a pulse frequency or duty cycle of the light signal emitted from the light source.

7. A method of manufacture comprising:
providing a substrate;
forming a photodetector within or on the substrate, wherein the photodetector is arranged to detect a light signal emitted from a light source comprising a laser upon the light signal being reflected from one or more objects in an external environment and irradiating a top surface of the photodetector; and
performing a processing step that mitigates dark current arising from minority carriers photoexcited in the substrate based on the light signal emitted from the light source.

8. The method of claim 7 , wherein performing the processing step that mitigates dark current comprises thinning the substrate by removing a portion of the substrate, thereby reducing a depth of the substrate to less than or equal to 100 times a diffusion length of a minority carrier within the substrate.

9. The method of claim 7 , wherein performing the processing step that mitigates dark current comprises producing crystallographic defects within the substrate that allow for recombination of electrons and holes.

10. The method of claim 7 , wherein performing the processing step that mitigates dark current comprises defining a band structure based on a material composition of the substrate and the photodetector.

11. The method of claim 10 ,
wherein the band structure results in an electric field that extends beyond a depletion region of the photodetector based on a curvature of a conduction band or a valence band of the band structure beyond the depletion region of the photodetector, and
wherein the electric field is configured to induce a drift current that accelerates minority carriers toward the depletion region of the photodetector when minority carriers are photoexcited in the substrate based on the light signal emitted from the light source.

12. The method of claim 10 ,
wherein the band structure comprises a potential barrier, and
wherein the potential barrier is configured to prevent minority carriers photoexcited in the substrate from reaching a depletion region of the photodetector due to diffusion.

13. The method of claim 10 ,
wherein the band structure comprises a potential well, and
wherein the potential well is configured to prevent minority carriers photoexcited in the substrate from reaching a depletion region of the photodetector due to diffusion.

14. The method of claim 10 ,
wherein the substrate comprises a heterostructure,
wherein the heterostructure comprises a first material,
wherein the first material has a band gap larger than a photon energy associated with the light signal emitted from the light source, and
wherein the first material is present within the substrate at a first depth within the substrate to define a maximum absorption depth for the light signal emitted from the light source.

15. The method of claim 7 , further comprising flip-chip bonding the substrate and the photodetector to one or more electrodes used to bias the photodetector such that the photodetector is arranged to detect the light signal from the light source upon the light signal being reflected from the one or more objects in the external environment and irradiating a second surface of the substrate.

Assignees

• Waymo Llc

Inventors

• Onal Caner
• Verghese Simon
• Droz Pierre-Yves

Classifications

• H10F71/131

  Recrystallisation; Crystallization of amorphous or microcrystalline semiconductors · CPC title

• H10F71/00

  Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00) · CPC title

• H10F77/14 Primary

  Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies · CPC title

• H10F30/225 Primary

  the potential barrier working in avalanche mode, e.g. avalanche photodiodes · CPC title

• H10F77/147

  Shapes of bodies · CPC title