# US 8,569,739 B2 · Chemically-etched nanostructures and related devices

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- Number: US 8,569,739 B2
- Document ID: US8569739B2
- Status: Granted
- Kind: B2
- Application number: 13/314,688
- Filed: 2011-12-08
- Published: 2012-06-21
- Granted: 2013-10-29
- Earliest claimed: 2010-12-16
- Assignees: California Institute of Technology
- Applicants: Seheon Kim; Axel Scherer; Jingqing Huang; Dong Yoon Oh
- Inventors: Seheon Kim; Axel Scherer; Jingqing Huang; Dong Yoon Oh
- Web page: https://patentgrep.com/patent/US8569739B2

## CPC

- G02B 6/1225: {comprising photonic band-gap structures or photonic lattices}
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- B82Y 40/00: Manufacture or treatment of nanostructures
- G02F 1/01708: {in an optical wavequide structure}
- H01S 5/11: Comprising a photonic bandgap structure
- G02F 2202/32: Photonic crystals
- H01S 5/2081: {using special etching techniques}
- H01S 5/3412: {quantum box or quantum dash}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A method of etching active quantum nanostructures provides the step of laterally etching of an intermediate active quantum nanostructure layer interposed between cladding layers. The lateral etching can be carried out on at least one side of the intermediate active quantum nanostructure layer selectively, with respect to the cladding layers to define at least one lateral recess or spacing in the intermediate active quantum nanostructure layer and respective lateral protrusions of cladding layers protruding with respect to the intermediate active quantum nanostructure layer. This method can be applied to create devices including active quantum nanostructures such as, for example, three-dimensional photonic crystals, a photonic crystal double-slab and a photonic crystal laser.

## Claims

### Claim 1

A method of etching active quantum nanostructures, the method comprising:
providing a wafer structure including a first cladding layer and a second cladding layer, the wafer structure further comprising an intermediate active quantum nanostructure layer interposed between the first cladding layer and the second cladding layer; and
laterally etching the intermediate active quantum nanostructure layer on at least one side of the intermediate active quantum nanostructure layer selectively with respect to the first cladding layer and second cladding layer to define at least one lateral recess in the intermediate active quantum nanostructure layer and respective lateral protrusions of the first cladding layer and the second cladding layer protruding with respect to the intermediate active quantum nanostructure layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein the laterally etching is laterally wet chemically etching.

### Claim 3 (depends on 1)

The method of claim 1, wherein the intermediate active quantum nanostructure layer is laterally etched on all sides to define a single central zone of the intermediate active quantum nanostructure layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the wafer structure includes an array of air-holes defined in a semiconductor slab.

### Claim 5 (depends on 1)

The method of claim 1, wherein the intermediate active quantum nanostructure layer is a two-dimensional photonic-crystal structure.

### Claim 6 (depends on 1)

The method of claim 1, wherein as the lateral etching proceeds, the lateral etching of the intermediate active quantum nanostructure layer leaves an array of dot-like structures.

### Claim 7 (depends on 6)

The method of claim 6, wherein further etching of intermediate active quantum nanostructure layer removes remaining quantum dot structures.

### Claim 8 (depends on 7)

The method of claim 7, wherein after the further etching, the intermediate active quantum nanostructure layer is shaped as a plurality of columns or piles, spaced apart from one another at regular distance and interposed between the first cladding layer and the second cladding layer.

### Claim 9 (depends on 7)

The method of claim 7, wherein after the further etching, the intermediate active quantum nanostructure layer is shaped as a disk interposed between the first cladding layer and the second cladding layer.

### Claim 10 (depends on 1)

The method of claim 1, wherein the wafer structure includes one-dimensional photonic-crystals.

### Claim 11 (depends on 1)

The method of claim 1, wherein the intermediate active quantum nanostructure layer includes quantum wells, vertically stacked quantum dots or single quantum dots.

### Claim 12 (depends on 1)

The method of claim 1, wherein the laterally etching is laterally angled etching.

### Claim 13

A wafer structure comprising:
a first cladding layer and a second cladding layer;
an intermediate active quantum nanostructure layer interposed between the first cladding layer and the second cladding layer; and
at least one laterally etched recess made on one side of the wafer structure in the region of the intermediate active quantum nanostructure layer, said lateral etched recess defining a lateral protrusion of the first cladding layer and a lateral protrusion of the second cladding layer protruding with respect to the intermediate active quantum nanostructure layer.

### Claim 14 (depends on 13)

The wafer structure of claim 13, wherein the at least one laterally etched recess is a lateral wet-chemically etched recess.

### Claim 15 (depends on 13)

The wafer structure of claim 13, wherein the structure includes a two-dimensional photonic-crystal or a one-dimensional photonic crystal as a backbone structure.

### Claim 16

A method of creating three-dimensional photonic crystals, the method comprising:
providing a one-dimensional periodic structure including alternating layers of cladding and sacrificial layers;
performing lithography on a top surface of the one-dimensional periodic structure to define two-dimensional photonic crystal patterns, and to obtain a backbone structure including alternating void spaces and walls, each wall including said alternating layers of cladding and sacrificial layers; and
laterally etching at least one of said walls to partially remove the sacrificial layers sandwiched between two adjacent cladding layers and to obtain three-dimensional photonic crystals.

### Claim 17 (depends on 16)

The method of claim 16, wherein the laterally etching is laterally wet-chemically etching.

### Claim 18 (depends on 16)

The method of claim 16, wherein the laterally etching is laterally angled dry-etching.

### Claim 19 (depends on 16)

The method of claim 16, wherein the one dimensional periodic structure includes an embedded defect structure.

### Claim 20

Three-dimensional photonic crystals comprising a photonic crystal backbone structure including alternating void spaces and walls, each wall including alternating layers of cladding and sacrificial layers; the photonic crystal backbone structure further comprising laterally etched spacings in said sacrificial layers, wherein each laterally etched spacing surrounds a corresponding sacrificial layer, such that a portion of a top cladding layer overlaps a corresponding portion of an adjacent bottom cladding layer through said spacing.

### Claim 21

A photonic crystal double slab comprising two photonic crystal membranes, the two photonic crystal membranes overlapping one another and being spaced apart by means of an intermediate gap, wherein at least one of the two photonic crystal membranes include at least one intermediate active quantum nanostructure layer.

### Claim 22

A photonic crystal double slab comprising:
two photonic crystal membranes, the two photonic crystal membranes overlapping one another and being spaced apart by means of an intermediate gap; and
a current aperture structure between the two photonic crystal membranes,
wherein said intermediate gap is a lateral wet-chemically etched recess made in a sacrificial layer interposed between the two photonic crystal membranes.

### Claim 23

A photonic crystal laser comprising a photonic crystal double slab comprising two photonic crystal membranes, the two photonic crystal membranes overlapping one another and being spaced apart by means of an intermediate gap, wherein the photonic crystal double slab defines p-i-n or n-i-p doped layers.

### Claim 24

A method of fabricating a photonic crystal laser comprising:
providing two photonic crystal membranes, the two photonic crystal membranes overlapping one another;
interposing a sacrificial active quantum nanostructure between the two photonic crystal membranes;
laterally etching the sacrificial active quantum nanostructure to define a gap between the two photonic crystal membranes via microfabrication technologies;
depositing top electrodes using photolithography; and
etching holes through the two photonic crystal membranes using nano-fabrication technologies based on an electron-beam lithography.