Gallium Nitride Epitaxy by a Novel Hybrid VPE Technique

Gallium Nitride Epitaxy by a Novel Hybrid VPE Technique PDF

Author: David J. Miller

Publisher: Stanford University

Published: 2011

Total Pages: 131

ISBN-13:

DOWNLOAD EBOOK →

Gallium nitride is an important material for the production of next-generation visible and near-UV optical devices, as well as for high temperature electronic amplifiers and circuits; however there has been no bulk method for the production of GaN substrates for device layer growth. Instead, thick GaN layers are heteroepitaxially deposited onto non-native substrates (usually sapphire) by one of two vapor phase epitaxy (VPE) techniques: MOVPE (metalorganic VPE) or HVPE (hydride VPE). Each method has its strengths and weaknesses: MOVPE has precise growth rate and layer thickness control but it is slow and expensive; HVPE is a low-cost method for high rate deposition of thick GaN, but it lacks the precise control and heterojunction layer growth required for device structures. Because of the large (14%) lattice mismatch, GaN grown on sapphire requires the prior deposition of a low temperature MOVPE nucleation layer using a second growth process in a separate deposition system. Here we present a novel hybrid VPE system incorporating elements of both techniques, allowing MOVPE and HVPE in a single growth run. In this way, a thick GaN layer can be produced directly on sapphire. GaN growth commences as small (50-100 nm diameter) coherent strained 3-dimensional islands which coalesce into a continuous film, after which 2-dimensional layer growth commences. The coalescence of islands imparts significant stress into the growing film, which increases with the film thickness until catastrophic breakage occurs, in-situ. Additionally, the mismatch in thermal expansion rates induces compressive stress upon cooling from the growth temperature of 1025°C. We demonstrate a growth technique that mitigates these stresses, by using a 2-step growth sequence: an initial high growth rate step resulting in a pitted but relaxed film, followed by a low growth rate smoothing layer. As a result, thick (> 50 [Mu]m) and freestanding films have been grown successfully. X-ray rocking curve linewidth of 105 arcseconds and 10K PL indicating no "yellow" emission indicate that the material quality is higher than that produced by conventional MOVPE. By further modifying the hybrid system to include a metallic Mn source, it is possible to grow a doped semi-insulating GaN template for use in high frequency electronics devices.

Gallium Nitride Epitaxy by a Novel Hybrid VPE Technique

Gallium Nitride Epitaxy by a Novel Hybrid VPE Technique PDF

Author: David J. Miller

Publisher:

Published: 2011

Total Pages:

ISBN-13:

DOWNLOAD EBOOK →

Gallium nitride is an important material for the production of next-generation visible and near-UV optical devices, as well as for high temperature electronic amplifiers and circuits; however there has been no bulk method for the production of GaN substrates for device layer growth. Instead, thick GaN layers are heteroepitaxially deposited onto non-native substrates (usually sapphire) by one of two vapor phase epitaxy (VPE) techniques: MOVPE (metalorganic VPE) or HVPE (hydride VPE). Each method has its strengths and weaknesses: MOVPE has precise growth rate and layer thickness control but it is slow and expensive; HVPE is a low-cost method for high rate deposition of thick GaN, but it lacks the precise control and heterojunction layer growth required for device structures. Because of the large (14%) lattice mismatch, GaN grown on sapphire requires the prior deposition of a low temperature MOVPE nucleation layer using a second growth process in a separate deposition system. Here we present a novel hybrid VPE system incorporating elements of both techniques, allowing MOVPE and HVPE in a single growth run. In this way, a thick GaN layer can be produced directly on sapphire. GaN growth commences as small (50-100 nm diameter) coherent strained 3-dimensional islands which coalesce into a continuous film, after which 2-dimensional layer growth commences. The coalescence of islands imparts significant stress into the growing film, which increases with the film thickness until catastrophic breakage occurs, in-situ. Additionally, the mismatch in thermal expansion rates induces compressive stress upon cooling from the growth temperature of 1025°C. We demonstrate a growth technique that mitigates these stresses, by using a 2-step growth sequence: an initial high growth rate step resulting in a pitted but relaxed film, followed by a low growth rate smoothing layer. As a result, thick (> 50 [Mu]m) and freestanding films have been grown successfully. X-ray rocking curve linewidth of 105 arcseconds and 10K PL indicating no "yellow" emission indicate that the material quality is higher than that produced by conventional MOVPE. By further modifying the hybrid system to include a metallic Mn source, it is possible to grow a doped semi-insulating GaN template for use in high frequency electronics devices.

Gallium Nitride Remote Epitaxy

Gallium Nitride Remote Epitaxy PDF

Author: Kuan Qiao (Scientist in mechanical engineering)

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

DOWNLOAD EBOOK →

Silicon-based electronics devices and integrated circuits have been the backbone of most modern technology, the demands for smaller and faster electronics have pushed the material towards its physical limitations. Compound semiconductor materials are growing in importance because of their ability to offer superior performance across a wide range of applications in optoelectronics and power electronics. Unfortunately, the adoption of these new materials has been hindered by the lack of cost-effective epitaxial substrates and the difficulties in integrating with existing processes. Additionally, the rigid wafers pose major challenges to future flexible electronics and the heterogeneous integration of dissimilar materials. To overcome these limitations, a new layer transfer technology based on remote epitaxy is developed. Remote epitaxy takes advantage of the atomic thickness of the two-dimensional (2D) material so that the wafer covered by 2D material can still be the substrate for epitaxial growth. At the same time, the weak van der Waals interaction between the 2D material and the epitaxial layer allows the epitaxial layer to be mechanically exfoliated precisely at the 2D material interface. In this work, the mechanism of remote epitaxy is systematically investigated. This work demonstrates that the strength of remote interaction between the substrate and epitaxial layer through 2D material is determined by the ionicity of the bulk materials and the thickness of the 2D interlayer. The 2D interlayer is transparent to such remote interaction unless it possesses periodic polar bonds. The remote epitaxy of gallium nitride (GaN) is studied in depth. Freestanding GaN thin film with a threading dislocation density of 2.1×107 cm−2 and electron mobility of 254 cm2/(V·s) is demonstrated. The thin film is then transferred onto a host substrate and the original substrate can be reused without refurbishment. The process demonstrated in this work can significantly reduce the production cost of compound semiconductor devices by reusing the expensive wafers. The free-standing crystalline thin films obtained by remote epitaxy can also be monolithically integrated to accommodate existing processes or create novel heterogeneous structures.

The Growth of Gallium Nitride Films Via the Innovative Technique of Atomic Layer Epitaxy

The Growth of Gallium Nitride Films Via the Innovative Technique of Atomic Layer Epitaxy PDF

Author:

Publisher:

Published: 1989

Total Pages: 28

ISBN-13:

DOWNLOAD EBOOK →

This contract involves investigating the efficacy of atomic layer and molecular beam epitaxy techniques for the growth of GaN (a wide bandgap semiconductor). During this reporting period, work was extended to growth of materials in the Al-Ga-In-N solid solution series as well as pure AlN and InN, and heterostructures of these materials. In addition, work was begun on the growth of cubic boron nitride. The first reported heterostructures of cubic GaN/ AlN were produced. Work also continued on characterization of the cubic GaN already produced. Much improved material and higher growth rates were observed with the installation of a NCSU-designed, constructed, and commissioned electron cyclotron resonance plasma source. Epitaxial growth, Crystallography.

Hydride vapour phase epitaxy growth, crystal properties and dopant incorporation in gallium nitride

Hydride vapour phase epitaxy growth, crystal properties and dopant incorporation in gallium nitride PDF

Author: Patrick Hofmann

Publisher: BoD – Books on Demand

Published: 2018-08-15

Total Pages: 166

ISBN-13: 3752884924

DOWNLOAD EBOOK →

This dissertation employs doping to investigate basic gallium nitride (GaN) crystal properties and to solve challenges of the hydride vapour phase epitaxy (HVPE) growth process. Whereas the first chapter is a short introduction to the history of the GaN single crystal growth, the 2nd chapter introduces to current crystal growth techniques, discusses properties of the GaN material system and the resulting influence on the applicable crystal growth techniques. HVPE, as a vapour phase epitaxy crystal growth method will be explained in greater detail, with focus on the used vertical reactor and its capabilities for doping. The 3rd chapter then focusses on point defects in GaN, specifically on intentionally introduced extrinsic point defects used for doping purposes, i.e. to achieve p-type, n-type or semi-insulating behaviour. Different dopants will be reviewed before the diffusion of point defects in a solid will be discussed. The in-situ introduction of iron, manganese, and carbon during crystal growth is employed in chapter 4 to compensate the unintentional doping (UID) of the GaN crystals, and therefore to achieve truly semi-insulating behaviour of the HVPE GaN. However the focus of this chapter lies on the characterisation of the pyroelectric coefficient (p), as semi-insulating properties are a necessary requirement for the applied Sharp-Garn measurement method. The creation of tensile stress due to in-situ silicon doping during GaN crystal growth is the topic of the 5th chapter. The tensile stress generation effect will be reproduced and the strain inside the crystal will be monitored ex-situ employing Raman spectroscopy. The n-type doping is achieved by using a vapour phase doping line and a process is developed to hinder the tensile strain generation effect. The 6th chapter concentrates on the delivery of the doping precursor via a solid state doping line, a newly developed doping method. Similar to chapter 5, the doping line is characterised carefully before the germanium doping is employed to the GaN growth. The focus lies on the homogeneity of the germanium doping and it is compared compared to the silicon doping and the vapour phase doping line. Benefits and drawbacks are discussed in conjunction with the obtained results. The germanium doping via solid state doping line is applied to the HVPE GaN growth process to measure accurately growth process related properties unique to the applied set of GaN growth parameters.

Lanterna Rally - Theme by Grace Themes