# US 2013/0153856 A1 · Infrared led device with isolation and method of making

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2013/0153856 A1
- Document ID: US20130153856A1
- Status: Published application
- Kind: A1
- Application number: 13/327,142
- Filed: 2011-12-15
- Published: 2013-06-20
- Earliest claimed: 2011-12-15
- Assignees: U.S. Government as represented by the Secretary of the Amry
- Inventors: Naresh C. Das
- Web page: https://patentgrep.com/patent/US20130153856A1

## CPC

- H10W 90/00: Package configurations
- H10H 20/018: {Bonding of wafers}
- H10H 20/812: within the light-emitting regions, e.g. having quantum confinement structures
- H10H 20/824: comprising only Group III-V materials, e.g. GaP
- H10H 29/142: {Two-dimensional arrangements, e.g. asymmetric LED layout}
- H10W 72/252: {comprising solid metals or solid metalloids, e.g. PbSn, Ag or Cu}
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

An infrared LED device comprising a plurality of LED mesas; each mesa being approximately 25 to 500 microns separated by a gap of approximately 50 to 100 microns; each mesa having at least two indium contacts; a substrate; and a plurality of leads for connection to the contacts, whereby upon application of electrical power infrared light emission occurs. The method of making comprises providing a first substrate; using molecular beam epitaxy, growing a quantum well structure comprising alternating active and injection regions on the substrate; growing a thin p-type layer on the quantum well structure; etching the mesa area down to the substrate to form a plurality of mesas, forming first electrical contacts; deep etching to isolate each of the mesas; depositing first indium contacts on the mesas; providing a second substrate; depositing second electrical contacts; bonding the first and second substrates at the points of the electrical contacts.

## Claims

### Claim 1

An infrared LED device comprising:
a plurality of LED mesas; each mesa separated by a gap of approximately 50 to 100 microns; each mesa being from approximately 25 to 500 microns, plurality of indium contacts, each mesa having at least two contacts associated therewith; one positive and one ground contact,
a substrate;
a plurality of leads for connection to the positive and negative contacts,
whereby upon application of electrical power infrared light emission occurs.

### Claim 2 (depends on 1)

The device of claim 1 wherein the infrared LED device is a Type II superlattice which is mounted epi-side down and wherein the mesas are positioned in an array.

### Claim 3 (depends on 1)

The device of claim 1 wherein each LED mesa comprises alternating cascaded active/injection regions.

### Claim 4 (depends on 3)

The device of claim 3 wherein alternating cascaded active/injection regions comprise an InAs/GaInSb/ InAs ‘W’ quantum well active region preceded by n-type digitally graded InAs/Al(In)Sb injection region.

### Claim 5 (depends on 3)

The device of claim 3 wherein the n-type injection regions serve as the collector and emitter for the preceding and following InAs/GaInSb/InAs ‘W’ quantum well active regions.

### Claim 6 (depends on 4)

The device of claim 4 wherein the alternating active and injection regions structure is strain balanced and lattice matched to the GaSb substrate.

### Claim 7 (depends on 5)

The device of claim 5 wherein under a forward bias, electrons were injected from an injection region into the Ee level which is in the band gap region of the adjacent GaInSb layer, and the electrons in the Ee level are effectively blocked from directly tunneling out of the GaInSb and Al(In)Sb layers, they tend to relax to the hole state Eh in the adjacent valence band quantum well, resulting in photon emission.

### Claim 8

A method of making an infrared LED device;
providing a first substrate;
using molecular beam epitaxy, growing a quantum well structure comprising alternating active and injection regions on the substrate;
growing a thin p-type layer on the quantum well structure;
etching the mesa area down to the substrate to form a plurality of mesas, each mesa being separated by a separation region of approximately 50 to 100 microns; each mesa being from approximately 25 to 500 microns;
forming electrical contacts;
deep etching to isolate each of the mesas;
deposit first indium contacts on the upper surface of the mesas;
provide a second substrate;
forming electrically conducting lines and pads;
deposit second indium contacts on the upper surface of the gold pads;
bonding the fanout silicon substrate and the GaSb mesa structure such that first indium contacts are in contact with the second indium contacts.

### Claim 9 (depends on 8)

The method of claim 8 wherein the first substrate is GaSb and the second substrate is silicon.

### Claim 10 (depends on 8)

The method of claim 8 wherein the step of using molecular beam epitaxy to grow a quantum well structure comprises forming at least 30 alternating active and injection regions on the substrate, and further comprises the step of growing a 1.4 micron p-type layer on the quantum well structure.

### Claim 11 (depends on 8)

The method of claim 8 wherein the step of etching the mesa area down to the substrate to form a plurality of mesas comprises etching approximately 3 microns using reactive ion etching of the mesa area using a Cl2/Bcl3 gas mixture and etching down to the GaSb base to form a plurality of mesas, each mesa being separated by a separation region of approximately 50 to 100 microns; each mesa being from approximately 25 to 500 microns.

### Claim 12 (depends on 9)

The method of claim 9 further wherein the step of forming electrical contacts comprises:
depositing a silicon nitride layer on both the mesas and separation regions;
using photolithography to make a pattern for anode and cathode contacts;
etching the silicon nitride layer using dry etching;
depositing gold metal by electron beam evaporation technique to form the anode and cathode contacts.

### Claim 13 (depends on 8)

The method of claim 8 further wherein the step of deep etching comprises deep etching 20 microns to form a trench around the mesas for mechanical stability to form a GaSb mesa structure.

### Claim 14 (depends on 8)

The method of claim 8 wherein the steps of depositing the first and second indium contacts comprises depositing contacts approximately 5-10 microns.

### Claim 15 (depends on 8)

The method of claim 8 wherein the step of bonding the fanout silicon substrate and the GaSb mesa structure such that first indium contacts are in contact with the second indium contacts comprises:
flip-chip bonding the fanout silicon substrate and the GaSb mesa structure such that first indium contacts are in contact with the second indium contacts;
applying epoxy in the separation regions;
curing the epoxy.

### Claim 16 (depends on 8)

The method of claim 8 wherein the step of deep etching to isolate each of the mesas comprises removing a portion of the GaSb layer (up to approximately 475 microns to leave approximately 25 microns and chemical etching to isolate the mesas.

### Claim 17

A method of making an infrared LED device;
providing a substrate;
using molecular beam epitaxy, growing a quantum well structure comprising alternating active and injection regions on the substrate;
growing a thin p-type layer on the quantum well structure;
etching the mesa area down to the substrate to form a plurality of mesas, each mesa being separated by a separation region of approximately 50 to 100 microns; each mesa being from approximately 25 to 500 microns;
using photolithography to make a pattern for anode and cathode contacts;
etching the silicon nitride layer using dry etching;
depositing gold metal by electron beam evaporation technique to form the anode and cathode contacts;
deep etching (approximately 20 microns) to form a trench around the mesas for mechanical stability to form a GaSb mesa structure;
deposit first indium contacts (approximately 5-10 microns) on the upper surface of the mesas;
provide a silicon substrate;
deposit silicon dioxide on the substrate;
using a photolithographic technique, depositing gold metal to form gold metal lines and pads;
deposit second indium contacts (approximately 5-10 microns) on the upper surface of the gold pads;
flip-chip bonding the fanout silicon substrate and the GaSb mesa structure such that first indium contacts are in contact with the second indium contacts;
applying epoxy in the separation regions;
curing the epoxy at approximately 70 to 100 degrees Celsius for one to two hours;
removing a portion of the GaSb layer (up to approximately 475 microns to leave approximately 25 microns;
chemical etching the remaining 25 microns to isolate the mesas.