Nonpolar<i>a</i>-Plane AlGaN/GaN Heterostructure Field-Effect Transistors Grown on Freestanding GaN Substrate

Isobe, Yasuhiro; Ikki, Hiromichi; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Sugiyama, Tetsuya; Amano, Hiroshi; Imade, Mamoru; Kimura, Yasuo; Mori, Yusuke

doi:10.1143/apex.4.064102

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…At a first glance, 2D electron gas confined in a-plane of AlGaN/GaN[40] appears very similar to the present case of the 2DEG formed in a c-oriented wedge shaped GaN nanowall structure. However, unlike the present case, such a heterojunction lacks spatial inversion symmetry(SIA) leading to the existence of a net electric field.…”

supporting

confidence: 81%

Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

Deb

Bhasker

Thakur

et al. 2016

Sci Rep

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A novel route to achieve two dimensional (2D) carrier confinement in a wedge shaped wall structure made of a polar semiconductor has been demonstrated theoretically. Tapering of the wall along the direction of the spontaneous polarization leads to the development of charges of equal polarity on the two inclined facades of the wall. Polarization induced negative (positive) charges on the facades can push the electrons (holes) inward for a n-type (p-type) material which results in the formation of a 2D electron (hole) gas at the central plane and ionized donors (acceptors) at the outer edges of the wall. The theory shows that this unique mode of 2D carrier confinement can indeed lead to a significant enhancement of carrier mobility. It has been found that the reduced dimensionality is not the only cause for the enhancement of mobility in this case. Ionized impurity scattering, which is one of the major contributer to carrier scattering, is significantly suppressed as the carriers are naturally separated from the ionized centers. A recent experimental finding of very high electron mobility in wedge shaped GaN nanowall networks has been analyzed in the light of this theoretical reckoning.

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supporting

confidence: 81%

Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

Deb

Bhasker

Thakur

et al. 2016

Sci Rep

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“…Polarization-free nonpolar a-plane GaN layers have been extensively considered as an adequate material for high-performance GaN-based optoelectronic devices owing to the absence of the quantum-confined Stark effect (QCSE) along its orientation [ 1 , 2 ]. Nonpolar GaN-based electronic devices, including high-electron-mobility transistors (HEMT), Schottky diodes, and metal–oxide–semiconductor field-effect transistor (MOSFET) sensors have been investigated to achieve enhanced performance such as enhancement mode (normally-off), temperature-stable characteristics with less pronounced hysteresis, and high sensitivity [ 3 , 4 , 5 , 6 ]. Due to the lack of native bulk GaN, researchers have been investigating the growth of a-plane GaN with improved structural properties grown on foreign substrates, using metal organic vapor phase epitaxy (MOCVD), molecular beam epitaxy (MBE), or hydride vapor phase epitaxy (HVPE) [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Electronic Transport Mechanism for Schottky Diodes Formed by Au/HVPE a-Plane GaN Templates Grown via In Situ GaN Nanodot Formation

Lee

et al. 2018

Nanomaterials

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We investigate the electrical characteristics of Schottky contacts for an Au/hydride vapor phase epitaxy (HVPE) a-plane GaN template grown via in situ GaN nanodot formation. Although the Schottky diodes present excellent rectifying characteristics, their Schottky barrier height and ideality factor are highly dependent upon temperature variation. The relationship between the barrier height, ideality factor, and conventional Richardson plot reveals that the Schottky diodes exhibit an inhomogeneous barrier height, attributed to the interface states between the metal and a-plane GaN film and to point defects within the a-plane GaN layers grown via in situ nanodot formation. Also, we confirm that the current transport mechanism of HVPE a-plane GaN Schottky diodes grown via in situ nanodot formation prefers a thermionic field emission model rather than a thermionic emission (TE) one, implying that Poole–Frenkel emission dominates the conduction mechanism over the entire range of measured temperatures. The deep-level transient spectroscopy (DLTS) results prove the presence of noninteracting point-defect-assisted tunneling, which plays an important role in the transport mechanism. These electrical characteristics indicate that this method possesses a great throughput advantage for various applications, compared with Schottky contact to a-plane GaN grown using other methods. We expect that HVPE a-plane GaN Schottky diodes supported by in situ nanodot formation will open further opportunities for the development of nonpolar GaN-based high-performance devices.

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“…Sheet charges are naturally induced due to polarization effects on typical c-plane AlGaN/GaN structures. One of the solutions is utilizing non-polar m-plane [17][18][19] or a-plane [20][21][22] GaN because the non-polar planes do not induce polarization charge. E-mode m-plane AlGaN/GaN HFETs have recently been demonstrated with V th ¼ þ2 V 17) which is a higher V th than those obtained with other techniques.…”

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confidence: 99%

Enhancement-Mode $m$-plane AlGaN/GaN Heterojunction Field-Effect Transistors with +3 V of Threshold Voltage Using Al$_{2}$O$_{3}$ Deposited by Atomic Layer Deposition

Fujiwara

Yeluri

Denninghoff

et al. 2011

Appl. Phys. Express

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Enhancement-mode m-plane AlGaN/GaN heterojunction field-effect transistors were fabricated with an Al2O3 gate dielectric deposited by atomic layer deposition (ALD). A threshold voltage of +3 V and an on/off ratio of 4×106 were obtained, demonstrating excellent subthreshold region characteristics. These results were achieved using non-polar m-plane GaN, Al2O3 as a gate dielectric, and a recessed-gate structure. The devices exhibited 138 mA/mm of maximum drain–source current at a gate–source voltage (Vgs) of +7 V and 45 mS/mm of maximum transconductance at Vgs=+5 V. The interface state density (Dit) of Al2O3 and m-plane GaN was measured using the photo assisted capacitance–voltage method, showing a Dit of (1–2)×1012 cm-2 eV-1. These results indicate the potential of Al2O3 deposited by ALD on m-plane GaN for power switching devices.

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Nonpolara-Plane AlGaN/GaN Heterostructure Field-Effect Transistors Grown on Freestanding GaN Substrate

Cited by 8 publications

References 21 publications

Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

Polarization induced two dimensional confinement of carriers in wedge shaped polar semiconductors

Electronic Transport Mechanism for Schottky Diodes Formed by Au/HVPE a-Plane GaN Templates Grown via In Situ GaN Nanodot Formation

Enhancement-Mode $m$-plane AlGaN/GaN Heterojunction Field-Effect Transistors with +3 V of Threshold Voltage Using Al$_{2}$O$_{3}$ Deposited by Atomic Layer Deposition

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