# US 10,374,118 B2 · Silicon germanium photodetector apparatus and other semiconductor devices including curved-shape silicon germanium structures

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- Number: US 10,374,118 B2
- Document ID: US10374118B2
- Status: Granted
- Kind: B2
- Application number: 15/332,877
- Filed: 2016-10-24
- Published: 2017-02-09
- Granted: 2019-08-06
- Earliest claimed: 2015-06-30
- Assignees: Massachusetts Institute of Technology
- Applicants: Massachusetts Institute of Technology
- Inventors: Luca Alloatti; Rajeev Jagga Ram; Dinis Cheian
- Web page: https://patentgrep.com/patent/US10374118B2

## CPC

- H10F 71/1215: {comprising at least two Group IV elements, e.g. SiGe}
- G02B 6/12: of the integrated circuit kind (electric integrated circuits H10B, H10D84/00 - H10D89/00, H10F19/00, H10F39/00, H10H29/00, H10K19/00, H10K39/00, H10K59/00, H10N19/00, H10N39/00, H10N59/00, H10N69/00, H10N79/00, H10N89/00)
- G02B 6/12004: {Combinations of two or more optical elements}
- G02B 6/122: Basic optical elements, e.g. light-guiding paths
- G02B 6/131: {by using epitaxial growth (epitaxial growth for semiconductors H10P14/20)}
- G02B 6/1347: {using ion implantation (ion implantation in glass C03C23/0055; ion implantation in general C23C)}
- G02B 6/29338: {Loop resonators}
- G02B 6/30: for use between fibre and thin-film device
- G02B 6/4295: {coupling with semiconductor devices activated by light through the light guide, e.g. thyristors, phototransistors}
- H10F 30/221: the potential barrier being a PN homojunction
- H10F 30/2218: {the devices comprising active layers made of only Group IV-VI materials}
- H10F 30/245: {Bipolar phototransistors}
- H10F 77/1226: comprising multiple Group IV elements, e.g. SiC
- H10F 77/148: {Shapes of potential barriers}
- H10F 77/206: {for devices having potential barriers}
- H10F 77/40: Optical elements or arrangements (surface textures H10F77/70)
- H10F 77/413: {directly associated or integrated with the devices, e.g. back reflectors (directly associated or integrated with photovoltaic cells H10F77/42)}
- G02B 2006/12097: {Ridge, rib or the like}
- G02B 2006/12123: {Diode}
- H10D 30/798: {being provided in or under the channel regions}
- H10D 64/661: {the conductor comprising a layer of silicon contacting the insulator, e.g. polysilicon having vertical doping variation (having lateral variation in the gate structure H10D64/671)}
- H10D 84/0167: {Manufacturing their channels}
- H10D 84/0172: {Manufacturing their gate conductors}
- H10D 84/038: {using silicon technology, e.g. SiGe}
- Y02E 10/50: Photovoltaic [PV] energy
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Semiconductor devices, such as photonics devices, employ substantially curved-shaped Silicon-Germanium (SiGe) structures and are fabricated using zero-change CMOS fabrication process technologies. In one example, a closed-loop resonator waveguide-coupled photodetector includes a silicon resonator structure formed in a silicon substrate, interdigitated n-doped well-implant regions and p-doped well-implant regions forming multiple silicon p-n junctions around the silicon resonator structure, and a closed-loop SiGe photocarrier generation region formed in a pocket within the interdigitated n-doped and p-doped well implant regions. The closed-loop SiGe region is located so as to substantially overlap with an optical mode of radiation when present in the silicon resonator structure, and traverses the multiple silicon p-n junctions around the silicon resonator structure. Electric fields arising from the respective p-n silicon junctions significantly facilitate a flow of the generated photocarriers between electric contact regions of the photodetector.

## Claims

### Claim 1

A photodetector apparatus, comprising:
a silicon substrate;
a first plurality of n-doped well-implant regions formed in the silicon substrate;
a second plurality of p-doped well-implant regions formed in the silicon substrate and interdigitated with the first plurality of n-doped well-implant regions so as to form a plurality of silicon p-n junctions; and
a curved-shape Silicon Germanium (SiGe) region formed within both the first plurality of n-doped well-implant regions and the second plurality of p-doped well-implant regions such that the plurality of p-n junctions are contiguous with the curved-shaped SiGe region.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein a cross-sectional width of the SiGe region is less than or equal to 500 nanometers.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the SiGe region is p-doped and has a germanium content of 25 to 35 atomic percent.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising a silicon closed-loop structure formed in the silicon substrate to provide a resonator for an optical mode of radiation, wherein:
the first plurality of n-doped well-implant regions and the second plurality of p-doped well-implant regions are formed as a plurality of interdigitated spokes around the silicon closed-loop structure.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the silicon closed-loop structure is one of an ellipsis, a race track, and a ring.

### Claim 6 (depends on 4)

The apparatus of claim 4, wherein the SiGe region is located in the silicon closed-loop structure so as to substantially overlap with the optical mode of radiation when present in the silicon ring so as to generate photocarriers in the SiGe region.

### Claim 7 (depends on 4)

The apparatus of claim 4, wherein:
the silicon closed-loop structure is a silicon ring structure;
a cross-sectional width of the SiGe region is less than or equal to approximately 500 nanometers;
an outer radius of the silicon ring structure is approximately 5 micrometers; and
the SiGe region is disposed about 300 nanometers from the outer radius of, and within, the silicon ring structure.

### Claim 8 (depends on 4)

The apparatus of claim 4, further comprising:
a first electrode electrically coupled to the first plurality of n-doped well-implant regions; and
a second electrode electrically coupled to the second plurality of p-doped well-implant regions.

### Claim 9 (depends on 4)

The apparatus of claim 4, wherein each of the n-doped well-implant regions and the p-doped well-implant regions is shaped as a clove so as to reduce a parasitic capacitance associated with the plurality of p-n junctions, wherein a first end of the clove closest to an outer radius of the silicon ring structure has a larger width than a second end of the clove closest to an inner radius of the silicon ring structure.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein at least some of the n-doped and p-doped well-implant regions include a higher-dose doping in the second end of the clove to reduce a resistance of the well-implant regions.

### Claim 11 (depends on 10)

The apparatus of claim 10, further comprising a plurality of counter implants respectively disposed adjacent to the first end of each clove closest to the outer radius of the silicon ring so as to reduce free-carrier absorption loss in the resonator.

### Claim 12

A waveguide-coupled closed-loop resonator Silicon Germanium (SiGe) photodetector apparatus, comprising:
a silicon closed-loop optical resonator structure to support an optical mode of radiation;
a plurality of p-n silicon junctions formed in the silicon resonator structure by a first plurality of n-doped silicon regions and a second plurality of p-doped silicon regions; and
a curved-shaped closed-loop SiGe pocket formed in the silicon resonator structure and traversing the plurality of p-n silicon junctions,
wherein the SiGe pocket is disposed with respect to the silicon resonator structure such that the optical mode of radiation, when present, overlaps with the SiGe pocket to generate photocarriers in the SiGe pocket.

### Claim 13 (depends on 12)

The apparatus of claim 12, further comprising:
a first electric contact coupled to the first plurality of n-doped silicon regions and a second electric contact coupled to the second plurality of p-doped silicon regions,
wherein the SiGe pocket is disposed with respect to the plurality of p-n silicon junctions such that respective electric fields arising from the plurality of p-n silicon junctions significantly facilitate a flow of the generated photocarriers between the first electric contact and the second electric contact.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein the SiGe pocket is p-doped and has a germanium content of 25 to 35 atomic percent.

### Claim 15 (depends on 13)

The apparatus of claim 13, wherein the first plurality of n-doped silicon regions and the second plurality of p-doped silicon regions are formed as a plurality of interdigitated spokes around the silicon resonator structure.

### Claim 16 (depends on 13)

The apparatus of claim 13, wherein the silicon closed-loop structure is one of an ellipsis, a race track, and a ring.

### Claim 17 (depends on 13)

The apparatus of claim 13, wherein each of the n-doped silicon regions and the p-doped silicon regions is shaped as a clove so as to reduce a parasitic capacitance associated with the plurality of p-n junctions, and wherein a first end of the clove closest to an outer dimension of the silicon resonator structure has a larger width than a second end of the clove closest to an inner dimension of the silicon resonator structure.

### Claim 18 (depends on 17)

The apparatus of claim 17, wherein at least some of the n-doped and p-doped silicon regions include a higher-dose doping in the second end of the clove to reduce a resistance of the well-implant regions.

### Claim 19 (depends on 18)

The apparatus of claim 18, further comprising a plurality of counter implants respectively disposed adjacent to the first end of each clove closest to the outer dimension of the silicon resonator structure so as to reduce free-carrier absorption loss in the silicon resonator structure.

### Claim 20 (depends on 12)

The apparatus of claim 12, formed by a photodetector fabrication method, comprising:
A) using a zero-change Complimentary Metal-Oxide Semiconductor (CMOS) fabrication process technology to form the waveguide-coupled closed-loop resonator photodetector having the curved-shaped closed-loop Silicon-Germanium (SiGe), the first plurality of n-doped silicon regions, and the second plurality of p-doped silicon regions.

### Claim 21 (depends on 20)

The method of claim 20, wherein the zero-change CMOS fabrication process technology is a 45 nanometer 12SOI silicon-on-insulator (SOI) CMOS process technology.

### Claim 22 (depends on 20)

The method of claim 20, wherein A) comprises:
A1) forming the first plurality of n-doped silicon regions in a silicon substrate using at least one first conventional n-well layer of the CMOS fabrication process technology;
A2) forming the second plurality of p-doped silicon regions in the silicon substrate, and interdigitated with the first plurality of n-doped silicon regions, using at least one second conventional p-well layer of the CMOS fabrication process technology so as to form the plurality of p-n junctions;
A3) forming the curved-shaped pocket in the first plurality of n-doped silicon well-implant regions and the second plurality of p-doped silicon well-implant regions; and
A4) epitaxially growing the curved-shaped SiGe pocket, using a conventional PFET strain engineering layer of the CMOS fabrication process technology, such that the SiGe pocket traverses the plurality of p-n junctions.