Materials

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9 pages, 3099 KiB

Open AccessArticle

Ohmic Contact to n-GaN Using RT-Sputtered GaN:O

by Monika Maslyk, Pawel Prystawko, Eliana Kaminska, Ewa Grzanka and Marcin Krysko

Materials 2023, 16(16), 5574; https://doi.org/10.3390/ma16165574 - 11 Aug 2023

Cited by 1 | Viewed by 1058

One of the key issues in GaN-based devices is the resistivity and technology of ohmic contacts to n-type GaN. This work presents, for the first time, effective intentional oxygen doping of sputtered GaN films to obtain highly conductive n⁺-GaN:O films. We [...] Read more.

One of the key issues in GaN-based devices is the resistivity and technology of ohmic contacts to n-type GaN. This work presents, for the first time, effective intentional oxygen doping of sputtered GaN films to obtain highly conductive n⁺-GaN:O films. We have developed a novel and simple method to obtain these films. The method is based on the room temperature magnetron sputtering of a single crystal bulk GaN target doped with oxygen. The n⁺-GaN:O films exhibit a polycrystalline structure with a crack-free surface and a free electron concentration of 7.4 × 10¹⁸ cm³. Ohmic contact to GaN:Si with n⁺-GaN:O sub-contact layer achieves specific contact resistance of the order of 10⁻⁵ Ωcm² after thermal treatment. The obtained results are very promising for the development of the technology of a whole new class of ohmic contacts to n-GaN. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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11 pages, 3375 KiB

Open AccessArticle

AlGaN HEMT Structures Grown on Miscut Si(111) Wafers

by Alexei V. Sakharov, Dmitri S. Arteev, Evgenii E. Zavarin, Andrey E. Nikolaev, Wsevolod V. Lundin, Nikita D. Prasolov, Maria A. Yagovkina, Andrey F. Tsatsulnikov, Sergey D. Fedotov, Evgenii M. Sokolov and Vladimir N. Statsenko

Materials 2023, 16(12), 4265; https://doi.org/10.3390/ma16124265 - 8 Jun 2023

Viewed by 1073

Abstract

A complex study was performed on a set of AlGaN/GaN high-electron-mobility transistor structures grown by metalorganic vapor phase epitaxy on miscut Si(111) wafers with a highly resistive epitaxial Si layer to investigate the influence of substrate miscut on their properties. The results showed [...] Read more.

A complex study was performed on a set of AlGaN/GaN high-electron-mobility transistor structures grown by metalorganic vapor phase epitaxy on miscut Si(111) wafers with a highly resistive epitaxial Si layer to investigate the influence of substrate miscut on their properties. The results showed that wafer misorientation had an influence on the strain evolution during the growth and surface morphology, and could have a strong impact on the mobility of 2D electron gas, with a weak optimum at 0.5° miscut angle. A numerical analysis revealed that the interface roughness was a main parameter responsible for the variation in electron mobility. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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10 pages, 3745 KiB

Open AccessArticle

Effect of High-Pressure GaN Nucleation Layer on the Performance of AlGaN/GaN HEMTs on Si Substrate

by You-Chen Weng, Ming-Yao Hsiao, Chun-Hsiung Lin, Yu-Pin Lan and Edward-Yi Chang

Materials 2023, 16(9), 3376; https://doi.org/10.3390/ma16093376 - 26 Apr 2023

Viewed by 1313

Abstract

A high-pressure (HP) GaN nucleation layer (NL) was inserted between AlGaN buffer and an unintentionally doped (UID) GaN layer of an AlGaN/GaN HEMT on Si. The XRD and TEM showed that when the V/III ratio was optimized during the HP-GaN NL growth, the [...] Read more.

A high-pressure (HP) GaN nucleation layer (NL) was inserted between AlGaN buffer and an unintentionally doped (UID) GaN layer of an AlGaN/GaN HEMT on Si. The XRD and TEM showed that when the V/III ratio was optimized during the HP-GaN NL growth, the edge dislocation density in the HP-GaN NL layer could be reduced significantly. Experimental results exhibited a lower off-state leakage current, higher maximum I_D and G_m (corresponding to 22.5% and 21.7% improvement, respectively), and lower on-state resistance. These results demonstrate that the electrical properties of the AlGaN/GaN HEMT can be improved through the insertion of a HP-GaN NL. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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10 pages, 5490 KiB

Open AccessEditor’s ChoiceArticle

The Heteroepitaxy of Thick β-Ga₂O₃ Film on Sapphire Substrate with a β-(Al_xGa_1−x)₂O₃ Intermediate Buffer Layer

by Wenhui Zhang, Hezhi Zhang, Song Zhang, Zishi Wang, Litao Liu, Qi Zhang, Xibing Hu and Hongwei Liang

Materials 2023, 16(7), 2775; https://doi.org/10.3390/ma16072775 - 30 Mar 2023

Cited by 1 | Viewed by 1594

Abstract

A high aluminum (Al) content β-(Al_xGa_1−x)₂O₃ film was synthesized on c-plane sapphire substrate using the gallium (Ga) diffusion method. The obtained β-(Al_xGa_1−x)₂O₃ film had an average thickness [...] Read more.

A high aluminum (Al) content β-(Al_xGa_1−x)₂O₃ film was synthesized on c-plane sapphire substrate using the gallium (Ga) diffusion method. The obtained β-(Al_xGa_1−x)₂O₃ film had an average thickness of 750 nm and a surface roughness of 2.10 nm. Secondary ion mass spectrometry results indicated the homogenous distribution of Al components in the film. The Al compositions in the β-(Al_xGa_1−x)₂O₃ film, as estimated by X-ray diffraction, were close to those estimated by X-ray photoelectron spectroscopy, at ~62% and ~61.5%, respectively. The bandgap of the β-(Al_xGa_1−x)₂O₃ film, extracted from the O 1s core-level spectra, was approximately 6.0 ± 0.1 eV. After synthesizing the β-(Al_xGa_1−x)₂O₃ film, a thick β-Ga₂O₃ film was further deposited on sapphire substrate using carbothermal reduction and halide vapor phase epitaxy. The β-Ga₂O₃ thick film, grown on a sapphire substrate with a β-(Al_xGa_1−x)₂O₃ buffer layer, exhibited improved crystal orientation along the (-201) plane. Moreover, the scanning electron microscopy revealed that the surface quality of the β-Ga₂O₃ thick film on sapphire substrate with a β-(Al_xGa_1−x)₂O₃ intermediate buffer layer was significantly improved, with an obvious transition from grain island-like morphology to 2D continuous growth, and a reduction in surface roughness to less than 10 nm. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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14 pages, 12535 KiB

Open AccessArticle

Effect of Electro-Thermo-Mechanical Coupling Stress on Top-Cooled E-Mode AlGaN/GaN HEMT

by Jie Jiang, Qiuqi Chen, Shengdong Hu, Yijun Shi, Zhiyuan He, Yun Huang, Caixin Hui, Yiqiang Chen, Hao Wu and Guoguang Lu

Materials 2023, 16(4), 1484; https://doi.org/10.3390/ma16041484 - 10 Feb 2023

Cited by 3 | Viewed by 1702

Abstract

This work investigated the effects of single stress and electro-thermo-mechanical coupling stress on the electrical properties of top-cooled enhancement mode (E-mode) Aluminium Gallium Nitride/Gallium Nitride (AlGaN/GaN) high electron mobility transistor (HEMT) (GS66508T). Planar pressure, linear deformation, punctate deformation, environmental temperature, electro-thermal coupling, thermo-mechanical [...] Read more.

This work investigated the effects of single stress and electro-thermo-mechanical coupling stress on the electrical properties of top-cooled enhancement mode (E-mode) Aluminium Gallium Nitride/Gallium Nitride (AlGaN/GaN) high electron mobility transistor (HEMT) (GS66508T). Planar pressure, linear deformation, punctate deformation, environmental temperature, electro-thermal coupling, thermo-mechanical coupling, and electro-thermo-mechanical coupling stresses were applied to the device. It was found that different kinds of stress had different influence mechanisms on the device. Namely, excessive mechanical pressure/deformation stress caused serious, irrecoverable degradation of the device’s leakage current, with the gate leakage current (I_g) increasing by ~10⁷ times and the drain-to-source leakage current (I_dss) increasing by ~10⁶ times after mechanical punctate deformation of 0.5 mm. The device characteristics were not restored after the mechanical stress was removed. Compared with three mechanical stresses, environmental thermal stress had a greater influence on the device’s transfer characteristic and on-resistance (R_on) but far less influence on I_g and I_dss. As was expected, multiple stress coupled to the device promoted invalidation of the device. For more in-depth investigation, finite element simulation carried out with COMSOL was used to analyze the effect of electro-thermo-mechanical coupling stress on top-cooled E-mode AlGaN/GaN HEMT. The results of the experiments and simulation demonstrated that single and coupled stresses, especially mechanical stress coupled with other stresses, degraded the electrical properties or even caused irreversible damage to top-cooled E-mode AlGaN/GaN HEMT. Mechanical stress should be reduced as much as possible in the packaging design, transportation, storage, and application of top-cooled E-mode AlGaN/GaN HEMT. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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14 pages, 5736 KiB

Open AccessEditor’s ChoiceArticle

Structure and Thermal Stability of ε/κ-Ga₂O₃ Films Deposited by Liquid-Injection MOCVD

by Edmund Dobročka, Filip Gucmann, Kristína Hušeková, Peter Nádaždy, Fedor Hrubišák, Fridrich Egyenes, Alica Rosová, Miroslav Mikolášek and Milan Ťapajna

Materials 2023, 16(1), 20; https://doi.org/10.3390/ma16010020 - 20 Dec 2022

Cited by 8 | Viewed by 2417

Abstract

We report on crystal structure and thermal stability of epitaxial ε/κ-Ga₂O₃ thin films grown by liquid-injection metal–organic chemical vapor deposition (LI-MOCVD). Si-doped Ga₂O₃ films with a thickness of 120 nm and root mean square surface roughness of [...] Read more.

We report on crystal structure and thermal stability of epitaxial ε/κ-Ga₂O₃ thin films grown by liquid-injection metal–organic chemical vapor deposition (LI-MOCVD). Si-doped Ga₂O₃ films with a thickness of 120 nm and root mean square surface roughness of ~1 nm were grown using gallium-tetramethylheptanedionate (Ga(thd)₃) and tetraethyl orthosilicate (TEOS) as Ga and Si precursor, respectively, on c-plane sapphire substrates at 600 °C. In particular, the possibility to discriminate between ε and κ-phase Ga₂O₃ using X-ray diffraction (XRD) φ-scan analysis or electron diffraction analysis using conventional TEM was investigated. It is shown that the hexagonal ε-phase can be unambiguously identified by XRD or TEM only in the case that the orthorhombic κ-phase is completely suppressed. Additionally, thermal stability of prepared ε/κ-Ga₂O₃ films was studied by in situ and ex situ XRD analysis and atomic force microscopy. The films were found to preserve their crystal structure at temperatures as high as 1100 °C for 5 min or annealing at 900 °C for 10 min in vacuum ambient (<1 mBar). Prolonged annealing at these temperatures led to partial transformation to β-phase Ga₂O₃ and possible amorphization of the films. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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8 pages, 1116 KiB

Open AccessArticle

Scattering Analysis of AlGaN/AlN/GaN Heterostructures with Fe-Doped GaN Buffer

by Dmitri S. Arteev, Alexei V. Sakharov, Wsevolod V. Lundin, Evgenii E. Zavarin, Andrey E. Nikolaev, Andrey F. Tsatsulnikov and Viktor M. Ustinov

Materials 2022, 15(24), 8945; https://doi.org/10.3390/ma15248945 - 14 Dec 2022

Cited by 2 | Viewed by 1251

Abstract

The results of the study of the influence of Fe segregation into the unintentionally doped GaN channel layer in AlGaN/AlN/GaN heterostructures with Fe-doped GaN buffer layer on the electrical properties of two-dimensional electron gas are presented. A set of several samples was grown [...] Read more.

The results of the study of the influence of Fe segregation into the unintentionally doped GaN channel layer in AlGaN/AlN/GaN heterostructures with Fe-doped GaN buffer layer on the electrical properties of two-dimensional electron gas are presented. A set of several samples was grown by metal-organic vapor-phase epitaxy and characterized by the van der Pauw method. The dependence of concentration and mobility of the two-dimensional electron gas on the channel layer thickness was analyzed theoretically by self-consistent solving of 1D Poisson and Schrödinger equations and scattering rate calculations within the momentum relaxation time approximation. It was found that both concentration and mobility decreases were responsible for the increase in the sheet resistance in the structures with a thinner channel layer, with a drop in mobility being not only due to ionized impurity scattering, but also due to a combined effect of weakening of screening, lower carrier energy and change in form-factors on scattering by interface roughness, dislocations and polar optical phonons. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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8 pages, 2270 KiB

Open AccessEditor’s ChoiceArticle

The Effect of a Nucleation Layer on Morphology and Grain Size in MOCVD-Grown β-Ga₂O₃ Thin Films on C-Plane Sapphire

by Lauris Dimitrocenko, Gundars Strikis, Boris Polyakov, Liga Bikse, Sven Oras and Edgars Butanovs

Materials 2022, 15(23), 8362; https://doi.org/10.3390/ma15238362 - 24 Nov 2022

Cited by 5 | Viewed by 1657

Abstract

β-Ga₂O₃ thin films grown on widely available c-plane sapphire substrates typically exhibit structural defects due to significant lattice and thermal expansion mismatch, which hinder the use of such films in electronic devices. In this work, we studied the impact of [...] Read more.

β-Ga₂O₃ thin films grown on widely available c-plane sapphire substrates typically exhibit structural defects due to significant lattice and thermal expansion mismatch, which hinder the use of such films in electronic devices. In this work, we studied the impact of a nucleation layer on MOCVD-grown β-Ga₂O₃ thin film structure and morphology on a c-plane sapphire substrate. The structure and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, transmission and scanning electron microscopy, while the composition was confirmed by X-ray photoelectron spectroscopy and micro-Raman spectroscopy. It was observed that the use of a nucleation layer significantly increases the grain size in the films in comparison to the films without, particularly in the samples in which H₂O was used alongside O₂ as the oxygen source for the nucleation layer growth. Our study demonstrates that a nucleation layer can play a critical role in obtaining high quality β-Ga₂O₃ thin films on c-plane sapphire. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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9 pages, 3924 KiB

Open AccessArticle

Fabrication of Ga₂O₃ Schottky Barrier Diode and Heterojunction Diode by MOCVD

by Teng Jiao, Wei Chen, Zhengda Li, Zhaoti Diao, Xinming Dang, Peiran Chen, Xin Dong, Yuantao Zhang and Baolin Zhang

Materials 2022, 15(23), 8280; https://doi.org/10.3390/ma15238280 - 22 Nov 2022

Cited by 5 | Viewed by 1566

Abstract

In this article, we reported on a Ga₂O₃-based Schottky barrier diode and heterojunction diode from MOCVD. The Si-doped n-type Ga₂O₃ drift layer, grown by MOCVD, exhibited high crystal quality, flat surfaces, and uniform doping. The distribution [...] Read more.

In this article, we reported on a Ga₂O₃-based Schottky barrier diode and heterojunction diode from MOCVD. The Si-doped n-type Ga₂O₃ drift layer, grown by MOCVD, exhibited high crystal quality, flat surfaces, and uniform doping. The distribution of unintentional impurities in the films was studied. Then nickel Schottky barrier diode and p-NiO/n-Ga₂O₃ heterojunction diode were fabricated and measured. Without any electric field management structure, the Schottky barrier diode and heterojunction diode have specific resistances of 3.0 mΩ·cm² and 6.2 mΩ·cm², breakdown voltages of 380 V and 740 V, thus yielding power figures of merit of 48 MW·cm⁻² and 88 MW·cm⁻², respectively. Besides, both devices exhibit a current on/off ratio of more than 10¹⁰. This shows the prospect of MOCVD in power device manufacture. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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17 pages, 4370 KiB

Open AccessEditor’s ChoiceArticle

High-Energy Computed Tomography as a Prospective Tool for In Situ Monitoring of Mass Transfer Processes inside High-Pressure Reactors—A Case Study on Ammonothermal Bulk Crystal Growth of Nitrides including GaN

by Saskia Schimmel, Michael Salamon, Daisuke Tomida, Steffen Neumeier, Tohru Ishiguro, Yoshio Honda, Shigefusa F. Chichibu and Hiroshi Amano

Materials 2022, 15(17), 6165; https://doi.org/10.3390/ma15176165 - 5 Sep 2022

Cited by 2 | Viewed by 2351

Abstract

For the fundamental understanding and the technological development of the ammonothermal method for the synthesis and crystal growth of nitrides, an in situ monitoring technique for tracking mass transport of the nitride throughout the entire autoclave volume is desirable. The feasibility of using [...] Read more.

For the fundamental understanding and the technological development of the ammonothermal method for the synthesis and crystal growth of nitrides, an in situ monitoring technique for tracking mass transport of the nitride throughout the entire autoclave volume is desirable. The feasibility of using high-energy computed tomography for this purpose was therefore evaluated using ex situ measurements. Acceleration voltages of 600 kV were estimated to yield suitable transparency in a lab-scale ammonothermal setup for GaN crystal growth designed for up to 300 MPa operating pressure. The total scan duration was estimated to be in the order of 20 to 40 min, which was sufficient given the comparatively slow crystal growth speed in ammonothermal growth. Even shorter scan durations or, alternatively, lower acceleration voltages for improved contrast or reduced X-ray shielding requirements, were estimated to be feasible in the case of ammonoacidic growth, as the lower pressure requirements for this process variant allow for thinned autoclave walls in an adapted setup designed for improved X-ray transparency. Promising nickel-base and cobalt-base alloys for applications in ammonothermal reactors with reduced X-ray absorption in relation to the maximum operating pressure were identified. The applicability for the validation of numerical simulations of the growth process of GaN, in addition to the applicability of the technique to further nitride materials, as well as larger reactors and bulk crystals, were evaluated. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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9 pages, 3006 KiB

Open AccessEditor’s ChoiceArticle

Electrical and Thermal Characteristics of AlGaN/GaN HEMT Devices with Dual Metal Gate Structure: A Theoretical Investigation

by Yongfeng Qu, Ningkang Deng, Yuan Yuan, Wenbo Hu, Hongxia Liu, Shengli Wu and Hongxing Wang

Materials 2022, 15(11), 3818; https://doi.org/10.3390/ma15113818 - 27 May 2022

Cited by 5 | Viewed by 2030

Abstract

The electrical and thermal characteristics of AlGaN/GaN high-electron mobility transistor (HEMT) devices with a dual-metal gate (DMG) structure are investigated by electrothermal simulation and compared with those of conventional single-metal gate (SMG) structure devices. The simulations reveal that the DMG structure devices have [...] Read more.

The electrical and thermal characteristics of AlGaN/GaN high-electron mobility transistor (HEMT) devices with a dual-metal gate (DMG) structure are investigated by electrothermal simulation and compared with those of conventional single-metal gate (SMG) structure devices. The simulations reveal that the DMG structure devices have a 10-percent higher transconductance than the SMG structure devices when the self-heating effect is considered. In the meantime, employing the DMG structure, a decrease of more than 11% in the maximum temperature rise of the devices can be achieved at the power density of 6 W/mm. Furthermore, the peak in heat generation distribution at the gate edge of the devices is reduced using this structure. These results could be attributed to the change in the electric field distribution at the gate region and the suppression of the self-heating effect. Therefore, the electrical and thermal performances of AlGaN/GaN HEMT devices are improved by adopting the DMG structure. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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12 pages, 4733 KiB

Open AccessEditor’s ChoiceArticle

High-Frequency and High-Power Performance of n-Type GaN Epilayers with Low Electron Density Grown on Native Substrate

by Roman M. Balagula, Liudvikas Subačius, Justinas Jorudas, Vytautas Janonis, Pawel Prystawko, Mikolaj Grabowski and Irmantas Kašalynas

Materials 2022, 15(6), 2066; https://doi.org/10.3390/ma15062066 - 11 Mar 2022

Cited by 6 | Viewed by 2210

Abstract

The n-type GaN epilayers with low electron density were developed on a native substrate using the metalorganic vapour phase epitaxy method and investigated under pulsed electric fields until material breakdown and optically in the spectrum range from 0.1 THz to 60 THz [...] Read more.

The n-type GaN epilayers with low electron density were developed on a native substrate using the metalorganic vapour phase epitaxy method and investigated under pulsed electric fields until material breakdown and optically in the spectrum range from 0.1 THz to 60 THz at two temperatures of 77 K and 300 K. The epilayers demonstrated the low-field electron mobility and density values reaching up to 1021 cm²/V·s and 1.06 × 10¹⁶ cm⁻³ (at 300 K) and 2652 cm²/V·s and 0.21 × 10¹⁶ cm⁻³ (at 77 K), respectively. Maximum injected electric power value till the damage of the GaN epilayer was found to be up to 1.8 GW/cm³ and 5.1 GW/cm³ at 77 K and 300 K, respectively. The results indicate new practical possibilities of the GaN material controlled by an external electric field. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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10 pages, 2620 KiB

Open AccessArticle

The Effect of Heavy Fe-Doping on 3D Growth Mode and Fe Diffusion in GaN for High Power HEMT Application

by Jin-Ji Dai, Thi Thu Mai, Umeshwar Reddy Nallasani, Shao-Chien Chang, Hsin-I Hsiao, Ssu-Kuan Wu, Cheng-Wei Liu, Hua-Chiang Wen, Wu-Ching Chou, Chieh-Piao Wang and Luc Huy Hoang

Materials 2022, 15(6), 2058; https://doi.org/10.3390/ma15062058 - 10 Mar 2022

Cited by 2 | Viewed by 2126

Abstract

The high electron mobility transistor (HEMT) structures on Si (111) substrates were fabricated with heavily Fe-doped GaN buffer layers by metalorganic chemical vapor deposition (MOCVD). The heavy Fe concentrations employed for the purpose of highly insulating buffer resulted in Fe segregation and 3D [...] Read more.

The high electron mobility transistor (HEMT) structures on Si (111) substrates were fabricated with heavily Fe-doped GaN buffer layers by metalorganic chemical vapor deposition (MOCVD). The heavy Fe concentrations employed for the purpose of highly insulating buffer resulted in Fe segregation and 3D island growth, which played the role of a nano-mask. The in situ reflectance measurements revealed a transition from 2D to 3D growth mode during the growth of a heavily Fe-doped GaN:Fe layer. The 3D growth mode of Fe nano-mask can effectively annihilate edge-type threading dislocations and improve transfer properties in the channel layer, and consequently decrease the vertical leakage current by one order of magnitude for the applied voltage of 1000 V. Moreover, the employment of GaN:C film on GaN:Fe buffer can further reduce the buffer leakage-current and effectively suppress Fe diffusion. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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10 pages, 3685 KiB

Open AccessArticle

Refractive Index of Heavily Germanium-Doped Gallium Nitride Measured by Spectral Reflectometry and Ellipsometry

by Dario Schiavon, Robert Mroczyński, Anna Kafar, Grzegorz Kamler, Iryna Levchenko, Stephen Najda and Piotr Perlin

Materials 2021, 14(23), 7364; https://doi.org/10.3390/ma14237364 - 30 Nov 2021

Cited by 7 | Viewed by 3005

Abstract

Gallium nitride (GaN) doped with germanium at a level of 10²⁰ cm⁻³ is proposed as a viable material for cladding layers in blue- and green-emitting laser diodes. Spectral reflectometry and ellipsometry are used to provide evidence of a reduced index of [...] Read more.

Gallium nitride (GaN) doped with germanium at a level of 10²⁰ cm⁻³ is proposed as a viable material for cladding layers in blue- and green-emitting laser diodes. Spectral reflectometry and ellipsometry are used to provide evidence of a reduced index of refraction in such layers. The refractive-index contrast to undoped GaN is about 0.990, which is comparable to undoped aluminium gallium nitride (AlGaN) with an aluminium composition of 6%. Germanium-doped GaN layers are lattice-matched to native GaN substrates; therefore, they introduce no strain, cracks, and wafer bowing. Their use, in place of strained AlGaN layers, will enable significant improvements to the production process yield. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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