# US 9,041,027 B2 · Methods of producing free-standing semiconductors using sacrificial buffer layers and recyclable substrates

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- Number: US 9,041,027 B2
- Document ID: US9041027B2
- Status: Granted
- Kind: B2
- Application number: 13/990,756
- Filed: 2010-12-01
- Published: 2013-10-03
- Granted: 2015-05-26
- Earliest claimed: 2010-12-01
- Assignees: Alliance for Sustainable Energy, LLC
- Applicants: Aaron Joseph Ptak; Yong Lin; Andrew Norman; Kirstin Alberi
- Inventors: Aaron Joseph Ptak; Yong Lin; Andrew Norman; Kirstin Alberi
- Web page: https://patentgrep.com/patent/US9041027B2

## CPC

- H10P 14/2921: {being crystalline insulating materials}
- C30B 23/025: {characterised by the substrate}
- C30B 25/183: {being provided with a buffer layer, e.g. a lattice matching layer}
- C30B 29/40: AIIIBV compounds {wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi}
- H10D 62/40: Crystalline structures
- H10P 14/3202: {Materials thereof}
- H10P 14/3241: {being conductive materials}
- H10P 14/3402: {characterised by the chemical composition}
- H10P 14/3416: {Nitrides}
- H10P 14/3418: {Phosphides}
- H10P 14/3421: {Arsenides}
- H10P 14/3431: {Selenides}
- H10P 14/38: {characterised by treatments done after the formation of the materials}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a spinel substrate using a sacrificial buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The sacrificial buffer material and semiconductor materials may be deposited using lattice-matching epitaxy or coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The sacrificial buffer layer may be dissolved using an epitaxial liftoff technique in order to separate the semiconductor device from the spinel substrate, and the spinel substrate may be reused in the subsequent fabrication of other semiconductor devices. The low-defect density semiconductor materials produced using this method result in the enhanced performance of the semiconductor devices that incorporate the semiconductor materials.

## Claims

### Claim 1

A method of producing a semiconductor device comprising:
growing a crystalline buffer material on a crystalline surface of a spinel substrate comprising MgAl2O4 by coincident site lattice-matching epitaxy to form a sacrificial buffer layer, wherein the crystalline buffer material comprises Al;
growing a first crystalline semiconductor material on the sacrificial buffer layer by lattice-matching epitaxy or coincident site lattice-matching epitaxy to form a first device layer comprising at least one of a III-V semiconductor material, a III-V semiconductor alloy, a II-VI semiconductor material, a II-VI semiconductor alloy, or mixtures thereof on the sacrificial buffer layer; and
separating the first device layer from the crystalline spinel substrate surface using an epitaxial liftoff method chosen from chemical etching of the crystalline buffer material or melting of the buffer material to produce a semiconductor device comprising the first device layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein at least one additional crystalline semiconductor material is grown on the first crystalline semiconductor material by lattice-matching epitaxy prior to separating the first device layer from the crystalline spinel substrate surface, the semiconductor device comprising the first device layer and the at least one additional crystalline semiconductor material.

### Claim 3 (depends on 1)

The method of claim 1, wherein the coincident site lattice-matching epitaxy and the lattice-matching epitaxy processes are conducted using molecular beam epitaxy.

### Claim 4 (depends on 1, 2)

The method of claim 1 or claim 2, wherein the semiconductor device is chosen from a photovoltaic solar cell, an LED, a laser, a transistor, or a light detector.

### Claim 5 (depends on 1)

The method of claim 1, further comprising recycling the spinel substrate for producing additional semiconductor devices.

### Claim 6

A semiconductor device comprising:
a crystalline spinel substrate comprising MgAl2O4;
a sacrificial buffer layer comprising crystalline Al, wherein the sacrificial buffer layer is coincident site lattice-matched to the crystalline spinel substrate; and
a first device layer comprising a first crystalline semiconductor material chosen from at least one of a III-V semiconductor material, a III-V semiconductor alloy, a II-VI semiconductor material, or a II-VI semiconductor alloy, wherein the first device layer is coincident site lattice-matched to the sacrificial buffer layer.

### Claim 7 (depends on 6)

The device of claim 6, further comprising at least one additional device layer comprising at least one additional crystalline semiconductor material chosen from at least one of III-V a semiconductor material, a III-V semiconductor alloy, a II-VI semiconductor material, or a II-VI semiconductor alloy, wherein the at least one additional device layer is lattice-matched to the first device layer.

### Claim 8 (depends on 7)

The method of claim 7, wherein the semiconductor device is a two junction PV solar cell, the first crystalline semiconductor material comprises GaInAlP alloy having a band gap of about 1.7-1.9 eV, and the at least one additional semiconductor material comprises InGaAs alloy having a band gap of about 1.15 eV.

### Claim 9 (depends on 6, 7)

The device of claim 6 or claim 7, wherein the semiconductor device is chosen from a photovoltaic solar cell, an LED, a laser, a transistor, or a light detector.

### Claim 10 (depends on 6)

The method of claim 6, wherein the semiconductor device is an LED and the first crystalline semiconductor material comprises InGaN having a band gap ranging between about 1.9 eV and about 2.5 eV.