The Nitride Crystal Growth Laboratory:Development and Plans

Paul T. FiniLead Researcher,

Nitride Crystal Growth Laboratory

Univ. of California, Santa BarbaraMaterials Department

Introduction

• Long-term goals of the Nitride Crystal Growth Laboratory include:

• ~340 nm LED/VCSEL to drive phosphors for white lighting

• ~280 nm LED/LD for remote bio-agent detection

• High-efficiency blue or green RC-LED for color mixing

• Truly bulk GaN substrates for light emitters with λ > 365 nm

• Truly bulk AlN substrates for light emitters with λ < 365 nm

Introduction (cont.)

• The Nitride Crystal Growth Laboratory was planned and built for three crystal growth techniques:

• MOCVD (Metalorganic Chemical Vapor Deposition)• Heterostructures: nanometer-level thickness control• Light-emitting (Al,In)GaN device structures

• HVPE (Hydride Vapor Phase Epitaxy)• Fast (> 100 µm/hr) growth rate• Free-standing (t > 200-300 µm) 2” GaN and AlN

• Ammonothermal Growth• Goal: truly bulk (1-2” φ) GaN and AlN single crystals

Growth Technique Interdependence

MOCVD

HVPE AMMONO

Low T

DD templa

tes, L

EO

Free

-stan

ding s

ubstr

ates

Bulk GaN or AlN substrate

Pure nutrient, seed on substrate

Bulk GaN or AlN substrate

Pure nutrient, free-standing seeds

Ammonothermal Growth of Bulk GaN

Milestones:1. Confirmation of fluid transport

growth2. Larger crystals3. Higher cyrstal quality

Growth mechanisms:1. Dissolution of nutrient into

supercritical ammonia2. Transport of Ga*N* up to the

seed crystal(s)3. Precipitation of GaN on the

seed(s)

Lab Layout

Laboratory Construction

Laboratory Construction (cont.)

Laboratory Construction (cont.)

Laboratory Construction (cont.)

HVPE results: C-plane GaN

AFM (z: 5nm scale)

RT PL

Present Status and Near-Term Goals

• MOCVD: GaN:Si, GaN:Mg, InGaN, AlGaN, AlN demonstratedØGrowth of high-quality AlN on sapphireØGrowth of AlN/GaN DBRs for RC-LED structures

• HVPE: thick c- and a-GaN films on sapphire demonstratedØOptimization of conditions for planar a-plane GaNØUse of buffer layers for strain (i.e. cracking) controlØOne-step lateral epitaxial overgrowth (LEO)

• Ammonothermal: small-scale autoclaves used for studies of mineralizer chemistryØLarger autoclave and containment cell being installedØ Seeded growth using various mineralizers

Personnel

• MOCVD growth, characterization:John Kaeding, Rajat Sharma, Amy Hanlon

• HVPE growth, characterization:Ben Haskell, Shigemasa Matsuda

• Ammonothermal synthesis:Tadao Hashimoto, Kenji Fujito

• VCSEL process development, Laser lift-off:Morgan Pattison, Tal Margalith, Kenji Fujito, Tetsuo Fujii

• AlN sublimation growth (planned):Edward Letts, Troy Baker