Influence of AlN nucleation layer on vertical breakdown characteristics for GaN‐on‐Si

Freedsman, Joseph J.; Watanabe, Akihide; Yamaoka, Yuya; Kubo, Toshiharu; Egawa, Takashi

doi:10.1002/pssa.201532601

Cited by 40 publications

(26 citation statements)

References 21 publications

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“…In our previous work , the existence of SiN x at AlN/Si interface caused the degradation of AlN crystalline quality. Consequently, high threading dislocation densities in low quality AlN provide the leakage paths leading to enhanced electric field in the dielectric layer , which increases the dielectric constant of the insulating AlN and the consequent AlN capacitance, resulting in the increase of RF loss. Moreover, lower crystalline quality induces higher roughness, which leads to an increase in the conductor loss of lines deposited on rough surface, contributing to the increased overall loss.…”

Section: Resultsmentioning

confidence: 99%

RF loss mechanisms in GaN‐based high‐electron‐mobility‐transistor on silicon: Role of an inversion channel at the AlN/Si interface

Luong¹,

Lumbantoruan²,

Chen³

et al. 2017

Physica Status Solidi (a)

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One of the epitaxial issues pertaining to the growth of AlGaN/ GaN HEMTs on Si is the decrease of parasitic losses that can adversely impact the RF device performances. We characterized the microwave losses in coplanar waveguides (CPWs) on GaN-based high-electron-mobility-transistors (HEMTs) and their buffer layers on Silicon substrate, up to 40 GHz. The RF losses depend not only on the crystalline quality but also on the residual tensile stress in AlN buffer, as well as its thickness.The mechanism of interfacial lossy channel induced by the piezoelectric field is discussed. Adopting a thin high-low-high temperature (HLH) AlN buffer can help to reduce the tensile stress leading to a reduction of RF losses. We suggest that a thinner p-type AlN and/or p-AlGaN-on-thin AlN near the interface can suppress the electron interfacial lossy channel, which helps the GaN-HEMT-on-HR Si to remain in a high frequency range and at high-temperature operation.

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Section: Resultsmentioning

confidence: 99%

RF loss mechanisms in GaN‐based high‐electron‐mobility‐transistor on silicon: Role of an inversion channel at the AlN/Si interface

Luong¹,

Lumbantoruan²,

Chen³

et al. 2017

Physica Status Solidi (a)

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“…c and d). According to our previous studies, this is crucial for achieving good crystal quality crack‐free structures as well as good electrical isolation with respect to the substrate . The threading dislocation density (TDD) can be deduced from the XRD line width .…”

Section: Methodsmentioning

confidence: 96%

Influence of metal-organic vapor phase epitaxy parameters and Si(111) substrate type on the properties of AlGaN/GaN HEMTs with thin simple buffer

Frayssinet¹,

Leclaire

Mohdad³

et al. 2016

Phys. Status Solidi A

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Phone: þ33 4 93 95 42 00, Fax: þ33 4 93 95 83 61The present work is dedicated to the study of the influence of metal-organic vapor phase epitaxy (MOVPE) growth conditions on the properties of AlGaN/GaN high electron mobility transistor (HEMT) heterostructures with thin simple buffer layers on Si(111). In a first series of samples grown on high resistivity silicon, the conditions were varied within the GaN buffer layer while kept unchanged for the AlN nucleation layer and HEMT barrier and cap layers. XRD and AFM revealed some differences in epilayers structural quality especially in case of excessive growth pressure or V/III ratio. Capacitancevoltage (CV) measurements revealed differences in the pinchoff regime of the two-dimensional electron gas (2DEG) located at the AlN/GaN interface. Except in one case, the buffer leakage current between isolated devices correlates with the pinch-off behavior. The majority of these structures exhibited sheet carrier densities of 1 Â 10 13 cm À2 and electron mobility between 1100 and 1400 cm 2 V À1 s À1 depending on the GaN channel growth conditions. The output and transfer characteristics (maximum drain currents and leakage currents) of the transistors are in agreement with the previous electrical characterizations. Thanks to the combination of structural and electrical characterizations we are then able to determine the optimized growth conditions for such HEMT structures. Compared with high resistivity silicon, we obtained better structural and electrical quality on conductive substrates. A 2DEG with an electron mobility of 1700 cm 2 V À1 s À1 has been achieved within a structure with a 0.5 mm thick buffer producing an off-state breakdown voltage of 117 V. This reveals the crucial role of the substrate surface properties on the resulting quality of the heterostructures.

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“…As shown in Figure 1 (left picture), the growth rapidly results in smooth and pit-free AlN films, which seems different from MOVPE. [9] Atomic Force Microscopy (AFM) shows surfaces with typical root mean square roughness (rms) well below 1 nm (typically <0.3 nm) at the micrometre scale. obtained on a thin 20 nm AlN film grown by MBE at 920 C on a high purity (float zone) Silicon substrate with a nominal resistivity ρ >5 kΩ cm.…”

Section: The Aln/si Interfacementioning

confidence: 99%

Influence of AlN Growth Temperature on the Electrical Properties of Buffer Layers for GaN HEMTs on Silicon

Cordier

Comyn

Frayssinet

et al. 2017

Physica Status Solidi (a)

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Despite the fact that a lower growth temperature is generally considered as a drawback for achieving high crystal quality, the necessity to reduce the nucleation temperature of AlN on Silicon has permitted Molecular Beam Epitaxy (MBE) to demonstrate high performance for GaN transistors operating at high frequency. Compared to Metal‐Organic Vapor Phase Epitaxy (MOVPE), the control of the interface between the AlN nucleation layer and the substrate is easier and the reduced growth temperature allows to obtain a more electrically resistive interface while keeping good crystal quality. Moreover, it is shown that further reducing the growth temperature within the nucleation and stress mitigating layers has a noticeable impact on the lateral and vertical buffer leakage currents. At the same time the buffer of MBE grown HEMT structures exhibits low RF propagation losses (below 0.5 dB mm−1 up to 70 GHz). Also, results obtained with structures regrown by MOVPE on MBE AlN‐on‐Si templates confirm that the thermal budget is critical for the resistivity of AlN/Si. On the other hand, the insertion of a 1.5 μm thick Al0.05Ga0.95N layer within a 2 μm HEMT structure significantly improves the vertical breakdown voltage up to 740 V permitting to compare favorably with MOVPE epilayers with similar total thickness.

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Influence of AlN nucleation layer on vertical breakdown characteristics for GaN‐on‐Si

Cited by 40 publications

References 21 publications

RF loss mechanisms in GaN‐based high‐electron‐mobility‐transistor on silicon: Role of an inversion channel at the AlN/Si interface

RF loss mechanisms in GaN‐based high‐electron‐mobility‐transistor on silicon: Role of an inversion channel at the AlN/Si interface

Influence of metal-organic vapor phase epitaxy parameters and Si(111) substrate type on the properties of AlGaN/GaN HEMTs with thin simple buffer

Influence of AlN Growth Temperature on the Electrical Properties of Buffer Layers for GaN HEMTs on Silicon

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