Improvement of the crystallinity of GaN epitaxial films grown on sapphire substrates due to the use of AlN quantum dot buffer layers

ABSTRACTAmmonia as nitrogen precursor has been used to grow III-V nitrides by molecular beam epitaxy (MBE) on c-plane sapphire substrates. The efficiency of NH3 has been evaluated allowing the determination of the actual V/III flux ratio used during the GaN growth. The effects of the V/III ratio variation on the GaN layer properties have been investigated by photoluminescence (PL), Hall measurements, atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS). It is found that a high V/III ratio leads to the best material quality. Optimized GaN thick buffer layers have been used to grow GaN/AlGaN quantum well (QW) heterostructures. Their PL spectra exhibit well resolved emission peaks for QW thicknesses varying from 3 to 15 monolayers. From the variation of the QW energies as a function of well width, a piezoelectric field of 450 kV/cm is deduced.

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Epitaxial GaN Layer Growth Using Nitrogen Enriched TiN Buffer Layers

MRS Proceedings ◽

10.1557/proc-0916-dd04-06 ◽

2006 ◽

Vol 916 ◽

Cited By ~ 1

Author(s):

Kazuhiro Ito ◽

Yu Uchida ◽

Sang-jin Lee ◽

Susumu Tsukimoto ◽

Yuhei Ikemoto ◽

...

Keyword(s):

Buffer Layer ◽

Light Emission ◽

Chemical Vapor ◽

Nucleation Site ◽

Layer Growth ◽

Buffer Layers ◽

Organic Chemical ◽

Nitrogen Enrichment ◽

Threading Dislocation ◽

Sapphire Substrates

AbstractAbout 20 years ago, the discovery of an AlN buffer layer lead to the breakthrough in epitaxial growth of GaN layers with mirror-like surface, using a metal organic chemical vapor deposition (MOCVD) technique on sapphire substrates. Since then, extensive efforts have been continued to develop a conductive buffer layer/substrate for MOCVD-grown GaN layers to improve light emission of GaN light-emitting diodes. In the present study, we produced MOCVD-grown, continuous, flat epitaxial GaN layers on nitrogen enriched TiN buffer layers with the upper limit of the nitrogen content of TiN deposited at room temperature (RT) on sapphire substrates. It was concluded that the nitrogen enrichment would reduce significantly the TiN/GaN interfacial energy. The RT deposition of the TiN buffer layers suppresses their grain growth during the nitrogen enrichment and the grain size refining must increase nucleation site of GaN. In addition, threading dislocation density in the GaN layers grown on TiN was much lower than that in the GaN layers grown on AlN.

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Halide Vapor Phase Epitaxy α‐ and ε‐Ga 2 O 3 Epitaxial Films Grown on Patterned Sapphire Substrates

physica status solidi (a) ◽

10.1002/pssa.201900892 ◽

2020 ◽

Vol 217 (14) ◽

pp. 1900892 ◽

Cited By ~ 8

Author(s):

Sevastian Shapenkov ◽

Oleg Vyvenko ◽

Evgeny Ubyivovk ◽

Oleg Medvedev ◽

Georgiy Varygin ◽

...

Keyword(s):

Vapor Phase ◽

Epitaxial Films ◽

Vapor Phase Epitaxy ◽

Sapphire Substrates ◽

Patterned Sapphire Substrates

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Free and Bound Excitons in GaN Epitaxial Films

MRS Proceedings ◽

10.1557/proc-449-497 ◽

1996 ◽

Vol 449 ◽

Cited By ~ 38

Author(s):

B.K. Meyer

Keyword(s):

Thermal Activation ◽

Chemical Nature ◽

Epitaxial Films ◽

Binding Energies ◽

Temperature Dependent ◽

Neutral Donor ◽

Exciton Localization ◽

Sapphire Substrates ◽

Shallow Donors ◽

Shallow Impurities

ABSTRACTWe report on photoluminescence experiments on hexagonal GaN epitaxial films grown on 6H-SiC and sapphire substrates by organo-metallic and hydide vapor phase epitaxy. At low temperatures we observe free and neutral donor bound exciton transitions which allow to establish properties of the free excitons and localisation energies of the bound excitons involving different shallow donors. From temperature dependent luminescence experiments thermal activation energies are determined which measure the exciton localization and donor binding energies. The localization energies of the excitons scale with the respective donor binding energies (Haynes rule). The inter-impurity transitions of neutral donors are observed in fourier transform infra-red absorption. Three shallow donors with binding energies of 34.7 meV, 55 meV and 58 meV can be seen. We present evidence for the chemical nature of the shallow impurities.

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Microstructural Evolution of Epitaxial LiNbO3 Thin Films Derived From Metal Alkoxide Solutions

MRS Proceedings ◽

10.1557/proc-202-439 ◽

1990 ◽

Vol 202 ◽

Cited By ~ 3

Author(s):

Keiichi Nashimoto ◽

Michael J. Cima ◽

Wendell E. Rhine

Keyword(s):

Thin Films ◽

Grain Growth ◽

Single Phase ◽

Sol Gel ◽

Precursor Solution ◽

Epitaxial Films ◽

Metal Alkoxide ◽

High Annealing Temperature ◽

Sapphire Substrates ◽

High Annealing

ABSTRACTThe evolution of the microstructure of sol-gel derived LiNbO3 thin films was investigated to understand the growth of epitaxial films. LiNbO3 films were prepared from a precursor solution of lithium ethoxide and niobium pentaethoxide. Prehydrolysis promoted the development of polycrys-talline LiNbO3 films, whereas nonhydrolysis produced solid-state epitaxial growth of LiNbO3 films on sapphire substrates. Although the films looked smooth after annealing at 400°C, the morphology of the films changed, depending on substrates and precursors, due to grain growth at high annealing temperature. Prehydrolysis of the alkoxides caused a decrease in the temperature at which grain growth occurred, whereas the film prepared from the nonhydrolyzed precursor on a sapphire substrate showed denser texture and contained abnormally large domains that appeared to be single phase.

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