Transport and optical properties of c-axis oriented wedge shaped GaN nanowall network grown by molecular beam epitaxy

Bhasker, H. P.; Thakur, Varun; Kesaria, Manoj; Shivaprasad, S. M.; Dhar, Subhabrata

doi:10.1063/1.4865647

Cited by 8 publications

(6 citation statements)

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“…Since the average tip-width t av has been found to increase with the decrease of h [see fig. 1(d)], the above observation is consistent with our earlier work 13 , where the samples grown with different values of t av are found to show a reduction of conductivity with increasing tip width. In the upper inset of Fig.…”

supporting

confidence: 92%

Two dimensional confinement of electrons in nanowall network of GaN leading to high mobility and phase coherence

Bhasker,

Thakur,

Shivaprasad

et al. 2014

Preprint

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Here, we report an alternative route to achieve two dimensional electron gas (2DEG) in a semiconductor structure. It has been shown that charge accumulation on the side facets can lead to the formation of 2DEG in a network of c-axis oriented wedge-shaped GaN nanowalls grown on c-plane sapphire substrate. Our study reveals that negative charges on the side-facets pushes the electron cloud inward resulting in the formation of 2DEG in the central plane parallel to the wall height. This confinement is evidenced from several orders of magnitude enhancement of electron mobility as compared to bulk, observation of weak localization effect in low temperature magneto-transport studies as well as the reduction of both the elastic and inelastic scattering rates with the average width of the walls. Importantly, the phase coherence length has been found to be as high as 20 µm, which makes the system potentially interesting for spintronics.Schrödinger and the Poisson equations are solved self-consistently taking into account the surface charge accumulation effect. The result indeed shows the 2D quantum confinement of electrons even for 40 nm of wall-width.

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confidence: 92%

Two dimensional confinement of electrons in nanowall network of GaN leading to high mobility and phase coherence

Bhasker,

Thakur,

Shivaprasad

et al. 2014

Preprint

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“…The study further predicts a very high electron mobility in this channel [16]. This prediction is also consistent with the experimental observation of high conductivity [17][18][19][20] and long phase coherence length [18,21,22] of electrons in the networks of wedge-shaped c-oriented GaN nanowalls. It will be interesting to understand the mechanism of spin transport through this channel.…”

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confidence: 89%

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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“…The study further predicts remarkably high electron mobility in this channel, which arises due to the natural separation of the electrons (in the middle) from the ionized donors (at the boundaries) 21 . These predictions are also supported by the experimental findings of high conductivity 23 – 26 and long phase coherence length 24 , 27 , 28 for electrons in networks of c -oriented GaN nano-wedges. Since the 2D confinement takes place deep inside the structure, the symmetry between the conduction and valence band is intact over the entire potential profile.…”

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confidence: 73%

Spin transport in polarization induced two-dimensional electron gas channel in c-GaN nano-wedges

Deb

Dhar

2021

Sci Rep

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A two-dimensional electron gas (2DEG), which has recently been shown to develop in the central vertical plane of a wedge-shaped c-oriented GaN nanowall due to spontaneous polarization effect, offers a unique scenario, where the symmetry between the conduction and valence band is preserved over the entire confining potential. This results in the suppression of Rashba coupling even when the shape of the wedge is not symmetric. Here, for such a 2DEG channel, relaxation time for different spin projections is calculated as a function of donor concentration and gate bias. Our study reveals a strong dependence of the relaxation rate on the spin-orientation and density of carriers in the channel. Most interestingly, relaxation of spin oriented along the direction of confinement has been found to be completely switched off. Upon applying a suitable bias at the gate, the process can be switched on again. Exploiting this fascinating effect, an electrically driven spin-transistor has been proposed.

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Transport and optical properties of c-axis oriented wedge shaped GaN nanowall network grown by molecular beam epitaxy

Cited by 8 publications

References 0 publications

Two dimensional confinement of electrons in nanowall network of GaN leading to high mobility and phase coherence

Two dimensional confinement of electrons in nanowall network of GaN leading to high mobility and phase coherence

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

Spin transport in polarization induced two-dimensional electron gas channel in c-GaN nano-wedges

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