High-mobility n−-GaN drift layer grown on Si substrates

Vertical GaN-on-Si devices are promising for the next-generation high-voltage power electronics with low cost and high efficiency. However, their applications are impeded by the limited thickness of crack-free GaN layers and high threading dislocation density (TDD) in the layer. Buffer layers are crucial for stress control while they usually behave with poor surface morphology, which causes early stress relaxation in GaN and limited thickness. Hereby, a terrace engineering approach for the buffer layers is proposed. Through tuning the supersaturation ratio, the terrace width can be manipulated and an atomically smooth AlGaN buffer layer can be realized, which effectively reduces the compressive stress relaxation and provides a firm foundation for thick GaN growth. As a result, a 7.5 μm thick GaN drift layer with TDD as low as 8.6 × 10 7 cm −2 is achieved on Si substrates. The room temperature electron mobility of the GaN drift layer can be raised up to 1210 cm 2 V −1 s −1 . The fabricated PiN diode shows a high breakdown voltage of 1058 V as well as a high on/off ratio of 10 12 . This work thus truly demonstrates the potential of high-performance and low-cost GaN-based electronic as well as optoelectronic devices on Si platforms.

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“…To the best of our knowledge, that value of mobility is also the highest reported so far for the GaN layer on Si. [ 52,56–58 ]…”

Section: Resultsmentioning

confidence: 99%

“…To the best of our knowledge, that value of mobility is also the highest reported so far for the GaN layer on Si. [52,[56][57][58] A quasi-vertical GaN-on-Si PiN diode was further fabricated based on this structure. Figure 5a shows the schematic diagram of the structure for the GaN PiN diode.…”

Section: Toward the High Performance Quasi-vertical Gan Pin Diodesmentioning

confidence: 99%

Terrace Engineering of the Buffer Layer: Laying the Foundation of Thick GaN Drift Layer on Si Substrates

Chen

Zhang

Liu

et al. 2023

Adv Elect Materials

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“…Silicon (Si) is a good candidate offering more advantages in comparison with SiC and sapphire, and is associated with crystalline perfection, a large area size, a low manufacturing cost, excellent electrical and thermal conductivity, being very suitable as a substrate for the growth of III-N materials and structures. Therefore, the growth of GaN-based materials and structures on Si has attracted considerable attention during this century [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Currently, the investigation into the growth and properties of GaN–Si materials and devices represents a hot topic in research and development (R&D) [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Optical, Structural, and Synchrotron X-ray Absorption Studies for GaN Thin Films Grown on Si by Molecular Beam Epitaxy

Feng,

Liu,

Xie

et al. 2024

Materials

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GaN on Si plays an important role in the integration and promotion of GaN-based wide-gap materials with Si-based integrated circuits (IC) technology. A series of GaN film materials were grown on Si (111) substrate using a unique plasma assistant molecular beam epitaxy (PA-MBE) technology and investigated using multiple characterization techniques of Nomarski microscopy (NM), high-resolution X-ray diffraction (HR-XRD), variable angular spectroscopic ellipsometry (VASE), Raman scattering, photoluminescence (PL), and synchrotron radiation (SR) near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. NM confirmed crack-free wurtzite (w-) GaN thin films in a large range of 180–1500 nm. XRD identified the w- single crystalline structure for these GaN films with the orientation along the c-axis in the normal growth direction. An optimized 700 °C growth temperature, plus other corresponding parameters, was obtained for the PA-MBE growth of GaN on Si, exhibiting strong PL emission, narrow/strong Raman phonon modes, XRD w-GaN peaks, and high crystalline perfection. VASE studies identified this set of MBE-grown GaN/Si as having very low Urbach energy of about 18 meV. UV (325 nm)-excited Raman spectra of GaN/Si samples exhibited the GaN E2(low) and E2(high) phonon modes clearly without Raman features from the Si substrate, overcoming the difficulties from visible (532 nm) Raman measurements with strong Si Raman features overwhelming the GaN signals. The combined UV excitation Raman–PL spectra revealed multiple LO phonons spread over the GaN fundamental band edge emission PL band due to the outgoing resonance effect. Calculation of the UV Raman spectra determined the carrier concentrations with excellent values. Angular-dependent NEXAFS on Ga K-edge revealed the significant anisotropy of the conduction band of w-GaN and identified the NEXAFS resonances corresponding to different final states in the hexagonal GaN films on Si. Comparative GaN material properties are investigated in depth.

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“…It was found that C concentrations down to 1.7 × 10 15 cm −3 were achieved when the chamber pressure was set at 200 mbar and the NH 3 partial pressure was maintained at ≈121 mbar for GaN‐on‐Si growth at a growth rate of 1 μm h −1 . [ 16 ] Suppressing carbon incorporation for GaN drift layer growth through quartz‐free hydride vapor phase epitaxy growth has also been investigated, achieving low effective doping levels while also maintaining high drift layer carrier mobility. [ 17 ] An alternative method, through above‐bandgap illumination, has also been demonstrated to suppress C N concentration through defect quasi‐Fermi‐level control.…”

Section: Introductionmentioning

confidence: 99%

Suppressing Carbon Incorporation in Metal–Organic Chemical Vapor Deposition GaN Using High‐Offcut‐Angled Substrates

Thirupakuzi Vangipuram,

Zhang,

Zhao

2023

Physica Rapid Research Ltrs

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Carbon (C) is a common impurity that acts as a compensator within GaN grown via metal–organic chemical vapor deposition (MOCVD). Reducing C in GaN will help reduce the compensation level and provide a route to achieve GaN with reliably low effective doping for high‐power device applications. GaN grown with fast growth rates on bulk GaN with various offcut angles via conventional‐MOCVD (C‐MOCVD) and laser‐assisted MOCVD (LA‐MOCVD) is compared and analyzed. C‐incorporation effects are compared through quantitative secondary‐ion mass spectroscopy analysis in GaN grown on GaN substrate with offcut angles of 4° and 0.3° toward m‐plane over a wide range of growth rates by C‐MOCVD and LA‐MOCVD. For both growth techniques investigated, a significant reduction in C‐incorporation is observed when a high‐offcut‐angle (4°) substrate is used as compared to a lower‐offcut‐angle (0.3°) substrate. With C‐MOCVD, at the fastest growth condition investigated (17.26 μm h−1 at 0.3°‐offcut, 15.25 μm h−1 at 4°‐offcut), a reduction in [C] by 21.2X is observed with an increase in the offcut angle from 0.3° to 4°. A 82.6X reduction in [C] is observed with the similar fast growth condition via LA‐MOCVD on GaN with 4° offcut angle (9.78 μm h−1) as compared to C‐MOCVD at 0.3° offcut angle (17.26 μm h−1).

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High-mobility n−-GaN drift layer grown on Si substrates

Cited by 8 publications

References 26 publications

Terrace Engineering of the Buffer Layer: Laying the Foundation of Thick GaN Drift Layer on Si Substrates

Terrace Engineering of the Buffer Layer: Laying the Foundation of Thick GaN Drift Layer on Si Substrates

Optical, Structural, and Synchrotron X-ray Absorption Studies for GaN Thin Films Grown on Si by Molecular Beam Epitaxy

Suppressing Carbon Incorporation in Metal–Organic Chemical Vapor Deposition GaN Using High‐Offcut‐Angled Substrates

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