III nitride semiconductor epitaxial substrate and III nitride semiconductor light emitting device, and methods of producing the same

• US 9,543,469 B2
• Filed: 08/06/2014
• Issued: 01/10/2017
• Est. Priority Date: 08/09/2013
• Status: Active Grant

• Current Assignee: Dowa Electronics Materials Co. Ltd. (DOWA Holdings Company Limited)
• Original Assignee: Dowa Electronics Materials Co. Ltd. (DOWA Holdings Company Limited)
• Inventors: Iwata, Masatoshi, Ooshika, Yoshikazu
• Primary Examiner(s): TAYLOR, EARL N
• Application Number:
  US14/904,207
• Publication Number:
  US 20160172534A1
• Time in Patent Office: 888 Days
• US Class Current: 1/1
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/68 Crystals with laminate structure, e.g. "superlattices"
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02576 N-type
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/12 with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/325 characterised by the doping materials
• CPC Class Codes: H01S 2301/173 The laser chip comprising special buffer layers, e.g. dislocation prevention or reduction
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A III nitride semiconductor epitaxial substrate having more excellent surface flatness is provided, in which the problems of crack formation and the double peaks in the shape of the EL spectrum are mitigated by employing appropriate conditions for Si doping on an AlN layer on a substrate; a III nitride semiconductor light emitting device; and methods of producing the same. A III nitride semiconductor epitaxial substrate has a substrate of which at least a surface portion is made of AlN, an undoped AlN layer formed on the substrate, an Si-doped AlN buffer layer formed on the undoped AlN layer, and a superlattice laminate formed on the Si-doped AlN buffer layer. The Si-doped AlN buffer layer has an Si concentration of 2.0×10¹⁹/cm³ or more and a thickness of 4 nm to 10 nm.

Claims

1. A III nitride semiconductor epitaxial substrate comprising:

a substrate of which at least a surface portion is made of AlN;

an undoped AlN layer formed on the substrate;

an Si-doped AlN buffer layer formed on the undoped AlN layer; and

a superlattice laminate formed on the Si-doped AlN buffer layer,

wherein the Si-doped AlN buffer layer has an Si concentration of 2.0×

10¹⁹/cm³ or more and a thickness in a range of 4 nm to 10 nm,

the superlattice laminate is formed by (i) stacking high Al-content layers represented by Al_xGa_1-xN, where x is an average composition in a crystal growth direction and x satisfies 0.9<

x≦

1, on the Si-doped AlN buffer layer and (ii) alternately stacking n sets, where n is an integer satisfying 4≦

n≦

10, of low Al-content layers and the high Al-content layers, each of the low Al-content layers being represented by Al_yGa_1-yN, where y is an average composition in the crystal growth direction and y satisfies 0<

y<

x, and

the first to (n−

2)th low Al-content layers from the Si-doped AlN buffer layer side have a first thickness, the (n−

1)th low Al-content layer has a second thickness larger than the first thickness, and the nth low Al-content layer has a third thickness equal to or larger than the second thickness.

2. The III nitride semiconductor epitaxial substrate according to claim 1, wherein the low Al-content layers are composition graded layers in which the Al composition decreases along the crystal growth direction.

3. The III nitride semiconductor epitaxial substrate according to claim 1, wherein the high Al-content layers are AlN layers, where x=1.

4. The III nitride semiconductor epitaxial substrate according to claim 1, wherein the third thickness is larger than the second thickness.

5. The III nitride semiconductor epitaxial substrate according to claim 1, wherein the high Al-content layers have the same thickness.

6. A III nitride semiconductor light emitting device comprising:

the III nitride semiconductor epitaxial substrate according to claim 1; and

an n-type cladding layer, an active layer, and a p-type cladding layer, in this order, on the substrate.

7. A method of producing a III nitride semiconductor epitaxial substrate, comprising the steps of:

forming an undoped AlN layer on a substrate of which at least a surface portion is made of AlN;

forming an Si-doped AlN buffer layer on the undoped AlN layer; and

forming a superlattice laminate on the Si-doped AlN buffer layer,

wherein in the step of forming the Si-doped AlN buffer layer, Si doping is performed such that an Si concentration of 2.0×

10¹⁹/cm³ or more is achieved and a thickness of the Si-doped AlN buffer layer is in a range of 4 nm to 10 nm,

the superlattice laminate is formed by (i) stacking high Al-content layers represented by Al_xGa_1-xN, where x is an average composition in a crystal growth direction and x satisfies 0.9<

x≦

1, on the Si-doped AlN buffer layer and (ii) alternately stacking n sets, where n is an integer satisfying 4≦

n≦

10, of low Al-content layers and the high Al-content layers, each of the low Al-content layers being represented by Al_yGa_1-yN, where y is an average composition in the crystal growth direction and y satisfies 0<

y<

x, and

the first to (n−

2)th low Al-content layers from the Si-doped AlN buffer layer side have a first thickness, the (n−

1)th low Al-content layer has a second thickness larger than the first thickness, and the nth low Al-content layer has a third thickness equal to or larger than the second thickness.

8. A method of producing a III nitride semiconductor light emitting device comprising a step of sequentially forming an n-type cladding layer, an active layer, and a p-type cladding layer on the III nitride semiconductor epitaxial substrate according to claim 7.