Characterization of a-plane GaN templates grown by HVPE and high efficiency deep UV emitting AlGaN/AlN MQWs grown by MBE on such templates

Adam Moldawer, Anirban Bhattacharyya, Lin Zhou, David Smith, Theodore D. Moustakas

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Thick GaN templates (>50 μm) were grown by hydride-vapor-phase epitaxy (HVPE) on the r-plane of sapphire. While X-ray diffraction indicates that the GaN grows with its a-plane parallel to the r-plane of sapphire, the surface has a triangular morphology of 120o, which is the result of the faster growth rate of the a-plane compared to the m-plane. Electron microscopy studies indicate that these GaN templates have a high concentration of threading defects (>1010 cm-2) and basal plane stacking faults (7x105 cm-1). Several identical deep-UV emitting Al0.7Ga0.3N/AlN multiple quantum wells (MQWs) were grown on such GaN templates by molecular-beam epitaxy (MBE). The wells were grown under more gallium than required by stoichiometry, which changes the growth mode from physical vapor deposition to liquid phase epitaxy. This growth mode leads to deep band structure potential fluctuations. The structure and microstructure of these MQWs were evaluated by transmission electron microscopy (TEM) and found to have even higher density of threading defects than the GaN template. In spite of this, the internal quantum efficiency (IQE) of these MQWs was estimated from the temperature dependence of the cathodoluminescence spectra to be 87%. This remarkable result was attributed to the deep band structure potential fluctuations introduced by the liquid-phase epitaxy growth mode as well as the high concentration of basal plane stacking faults.

Original languageEnglish (US)
Pages (from-to)585-589
Number of pages5
JournalPhysica Status Solidi (C) Current Topics in Solid State Physics
Volume11
Issue number3-4
DOIs
StatePublished - 2014

Fingerprint

vapor phase epitaxy
hydrides
molecular beam epitaxy
templates
quantum wells
liquid phase epitaxy
crystal defects
sapphire
defects
cathodoluminescence
gallium
quantum efficiency
stoichiometry
electron microscopy
vapor deposition
temperature dependence
transmission electron microscopy
microstructure
diffraction
x rays

Keywords

  • Hydride vapor phase epitaxy
  • Internal quantum efficiency
  • Non-polar AlGaN QWs
  • Non-polar GaN templates
  • Ultraviolet light emitting diodes

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Characterization of a-plane GaN templates grown by HVPE and high efficiency deep UV emitting AlGaN/AlN MQWs grown by MBE on such templates. / Moldawer, Adam; Bhattacharyya, Anirban; Zhou, Lin; Smith, David; Moustakas, Theodore D.

In: Physica Status Solidi (C) Current Topics in Solid State Physics, Vol. 11, No. 3-4, 2014, p. 585-589.

Research output: Contribution to journalArticle

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abstract = "Thick GaN templates (>50 μm) were grown by hydride-vapor-phase epitaxy (HVPE) on the r-plane of sapphire. While X-ray diffraction indicates that the GaN grows with its a-plane parallel to the r-plane of sapphire, the surface has a triangular morphology of 120o, which is the result of the faster growth rate of the a-plane compared to the m-plane. Electron microscopy studies indicate that these GaN templates have a high concentration of threading defects (>1010 cm-2) and basal plane stacking faults (7x105 cm-1). Several identical deep-UV emitting Al0.7Ga0.3N/AlN multiple quantum wells (MQWs) were grown on such GaN templates by molecular-beam epitaxy (MBE). The wells were grown under more gallium than required by stoichiometry, which changes the growth mode from physical vapor deposition to liquid phase epitaxy. This growth mode leads to deep band structure potential fluctuations. The structure and microstructure of these MQWs were evaluated by transmission electron microscopy (TEM) and found to have even higher density of threading defects than the GaN template. In spite of this, the internal quantum efficiency (IQE) of these MQWs was estimated from the temperature dependence of the cathodoluminescence spectra to be 87{\%}. This remarkable result was attributed to the deep band structure potential fluctuations introduced by the liquid-phase epitaxy growth mode as well as the high concentration of basal plane stacking faults.",
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AB - Thick GaN templates (>50 μm) were grown by hydride-vapor-phase epitaxy (HVPE) on the r-plane of sapphire. While X-ray diffraction indicates that the GaN grows with its a-plane parallel to the r-plane of sapphire, the surface has a triangular morphology of 120o, which is the result of the faster growth rate of the a-plane compared to the m-plane. Electron microscopy studies indicate that these GaN templates have a high concentration of threading defects (>1010 cm-2) and basal plane stacking faults (7x105 cm-1). Several identical deep-UV emitting Al0.7Ga0.3N/AlN multiple quantum wells (MQWs) were grown on such GaN templates by molecular-beam epitaxy (MBE). The wells were grown under more gallium than required by stoichiometry, which changes the growth mode from physical vapor deposition to liquid phase epitaxy. This growth mode leads to deep band structure potential fluctuations. The structure and microstructure of these MQWs were evaluated by transmission electron microscopy (TEM) and found to have even higher density of threading defects than the GaN template. In spite of this, the internal quantum efficiency (IQE) of these MQWs was estimated from the temperature dependence of the cathodoluminescence spectra to be 87%. This remarkable result was attributed to the deep band structure potential fluctuations introduced by the liquid-phase epitaxy growth mode as well as the high concentration of basal plane stacking faults.

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