Photodiode device monolithically integrating waveguide element with photodiode element type of optical waveguide

Patent metadata

Field	Value
Publication number	US-10585239-B2
Application number	US-201916290671-A
Country	US
Kind code	B2
Filing date	Mar 1, 2019
Priority date	Mar 2, 2018
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

A photodiode (PD) device that monolithically integrates a PD element with a waveguide element is disclosed. The PD device includes a conducting layer with a first region and a second region next to the first region, where the PD element exists in the first region, while, the waveguide element exists in the second region and optically couples with the PD element. The waveguide element includes a core layer and a cladding layer on the conducting layer, which forms an optical confinement structure. The PD element includes an absorption layer on the conducting layer and a p-type cladding layer on the absorption layer, which form another optical confinement structure. The absorption layer has a length at least 12 μm measured from the interface against the core layer.

First claim

What is claimed is:

1. A photodiode device, comprising:
a substrate providing a conducting layer doped with n-type impurities, the conducting layer having a first region and a second region next to the first region;
a waveguide element provided on the first region of the conducting layer, the waveguide element including:
a core layer provided on the conducting layer, and
a cladding layer provided on the core layer; and

a photodiode element provided on the second region of the conducting layer, the photodiode element being optically coupled with the waveguide element and including:
an absorption layer that is provided on the conducting layer and has a bandgap wavelength longer than 1612 nm, the absorption layer abutting against the core layer in the waveguide element, and
a p-type cladding layer that is provided on the absorption layer and doped with p-type impurities,

wherein the absorption layer in the photodiode element has a length at least 12 μm along an optical axis thereof measured from an interface against the core layer in the waveguide element.

2. The photodiode device according to claim 1 , further comprising a buffer layer that is provided on the conducting layer and extends from the first region to the second region,
wherein the core layer in the waveguide element is provided on the buffer layer, and
wherein the absorption layer in the photodiode element is provided on the buffer layer.

3. The photodiode device according to claim 2 ,
wherein the conducting layer is doped with silicon by density at least 1×10 17 cm −3 and the buffer layer is undoped or slightly doped with silicon by density of 1×10 16 cm −3 at most.

4. The photodiode device according to claim 2 ,
wherein the buffer layer has a thickness of 0.3 μm at most.

5. The photodiode device according to claim 2 ,
wherein the buffer layer has a bandgap wavelength shorter than a bandgap wavelength of the absorption layer but longer than or equal to a bandgap wavelength of the conducting layer.

6. The photodiode device according to claim 2 ,
wherein the photodiode element further includes an intermediate layer provided on the buffer layer in the second region of the conducting layer, the absorption layer being provided on the intermediate layer but the core layer being provided on the buffer layer.

7. The photodiode device according to claim 6 ,
wherein the intermediate layer is undoped or slightly doped with n-type impurities by density of 1×10 16 cm −3 at most.

8. The photodiode device according to claim 6 ,
wherein the absorption layer has a height measured from a top of the conducting layer to a middle between a top and a bottom of the absorption layer, where the height of the absorption layer is substantially equal to a height of the core layer measured from the top of the conducting layer to a middle between a top and a bottom of the core layer.

9. The photodiode device according to claim 6 ,
wherein the intermediate layer includes an upper layer and a lower layer, the upper layer being in contact with the absorption layer, the lower layer being in contact with the conducting layer, and
wherein the upper layer has a bandgap wavelength shorter than a bandgap wavelength of the absorption layer, the lower layer has a bandgap wavelength shorter than the bandgap wavelength of the upper layer but longer than a bandgap wavelength of the conducting layer.

10. The photodiode device according to claim 1 ,
wherein the photodiode element further includes an intermediate layer provided only in the second region of the conducting layer, the absorption layer being provided on the intermediate layer but the core layer in the waveguide element being provided on the conducting layer.

11. The photodiode device according to claim 10 ,
wherein the intermediate layer is undoped or slightly doped with n-type impurities by density of 1×10 16 cm −3 at most.

12. The photodiode device according to claim 10 ,
wherein the absorption layer has a height measured from a top of the conducting layer to a middle between a top and a bottom of the absorption layer, where the height of the absorption layer is substantially equal to a height of the core layer measured from the top of the conducting layer to a middle between a top and a bottom of the core layer.

13. The photodiode device according to claim 10 ,
wherein the intermediate layer includes an upper layer and a lower layer, the upper layer being in contact with the absorption layer, the lower layer being in contact with the conducting layer, and
wherein the upper layer has a bandgap wavelength shorter than a bandgap wavelength of the absorption layer, the lower layer has a bandgap wavelength shorter than the bandgap wavelength of the upper layer but longer than a bandgap wavelength of the conducting layer.

14. The photodiode device according to claim 2 ,
wherein the absorption layer is made of In x Ga 1-x As (0<x<1) and has a thickness of 0.1 to 0.4 μm.

15. A photodiode device that receives an optical signal and a local signal each having wavelengths substantially equal to each other, the optical signal containing two signal components each having phases different by 90°, the optical device comprising:
a substrate providing a conducting layer thereon, the conducting layer being doped with n-type impurities by density greater than 1×10 17 cm −3 ;
a buffer layer that is provided on the conducting layer,
an optical hybrid that receives the optical signal and the local signal, extracts the two signal components by performing interference between the optical signal and the local signal, and outputs the two signal components;
two photodiode elements each having absorption layers provided on the conducting layer and p-type cladding layers on the absorption layers; and
two waveguide elements that provide the two signal components extracted by the optical hybrid to the two photodiode elements, respectively, the two waveguide elements each having core layers on the conducting layer and cladding layers on the core layers,
wherein the absorption layers each have a length of at least 12 μm measured from respective interfaces against the waveguide elements along optical axes thereof,
wherein the core layers in the waveguide elements are each provided on the buffer layer, and
wherein the absorption layers in the photodiode elements are each provided on the buffer layer.

16. The photodiode device according to claim 15 ,
wherein the buffer layer is undoped or slightly doped with n-type impurities by density of 1×10 16 cm −3 at most.

17. The photodiode device according to claim 15 ,
wherein the buffer layer has a thickness 0.3 μm at most.

18. The photodiode device according to claim 15 ,
wherein the buffer layer has a bandgap wavelength shorter than a bandgap wavelength of the absorption layers but longer than or equal to a bandgap wavelength of the conducting layer.

Assignees

• Sedi Inc

Inventors

• Yoneda Yoshihiro
• Okimoto Takuya
• Sakurai Kenji

Classifications

• G02B2006/12078

  Gallium arsenide or alloys (GaAs, GaAlAs, GaAsP, GaInAs) · CPC title

• G02B6/12004 Primary

  Combinations of two or more optical elements · CPC title

• G02B6/4249

  comprising arrays of active devices and fibres · CPC title

• G02B6/4206

  Optical features (G02B6/4207, G02B6/421 take precedence) · CPC title

• H01L2924/10337

  Electricity · mapped topic