Defects in 
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 epilayers via molecular beam epitaxy and strategies for reducing them

Rice, Anthony D.; Park, Kwang-Wook; Hughes, Eamonn T.; Mukherjee, Kunal; Alberi, Kirstin

doi:10.1103/physrevmaterials.3.121201

Cited by 16 publications

(16 citation statements)

References 25 publications

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“…2(a) originates in a largely enhanced scattering that outweighs the expected increase in carrier mobilities due to the formation of bulk Dirac points and the gain in the charge carriers from self-doping. We note that studies on Cd 3 As 2 epilayers revealed a substantial effect of extended defects on electron mobilities [59]. Moreover, for epitaxial (112) Cd 3 As 2 films, a systematic decrease in Hall mobilities with the compressive in-plane strain ( s 0.5%) was observed [24].…”

Section: Discussionmentioning

confidence: 70%

Pressure-induced reconstructive phase transition inCd3As2

Gamża

Abrami

Gammond

et al. 2021

Phys. Rev. Materials

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Cadmium arsenide (Cd 3 As 2) hosts massless Dirac electrons in its ambient-condition tetragonal phase. We report x-ray diffraction and electrical resistivity measurements of Cd 3 As 2 upon cycling pressure beyond the critical pressure of the tetragonal phase and back to ambient conditions. We find that, at room temperature, the transition between the low-and high-pressure phases results in large microstrain and reduced crystallite size, both on rising and falling pressure. This leads to nonreversible electronic properties, including self-doping associated with defects and a reduction of the electron mobility by an order of magnitude due to increased scattering. This paper indicates that the structural transformation is sluggish and shows a sizable hysteresis of over 1 GPa. Therefore, we conclude that the transition is first-order reconstructive, with chemical bonds being broken and rearranged in the high-pressure phase. Using the diffraction measurements, we demonstrate that annealing at ∼200 • C greatly improves the crystallinity of the high-pressure phase. We show that its Bragg peaks can be indexed as a primitive orthorhombic lattice with a HP ≈ 8.68 Å, b HP ≈ 17.15 Å, and c HP ≈ 18.58 Å. The diffraction study indicates that, during the structural transformation, a new phase with another primitive orthorhombic structure may also be stabilized by deviatoric stress, providing an additional venue for tuning the unconventional electronic states in Cd 3 As 2 .

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Section: Discussionmentioning

confidence: 70%

Pressure-induced reconstructive phase transition inCd3As2

Gamża

Abrami

Gammond

et al. 2021

Phys. Rev. Materials

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show abstract

“…[13] High-quality thin films of Cd 3 As 2 have been grown by molecular beam epitaxy (MBE) and epitaxial integration of high-mobility Cd 3 As 2 films with III-V semiconductors has been demonstrated. [14][15][16] Despite this progress, the potential of 3D topological semimetals for high-speed electronics remains underexplored. [17,18] In this Article, we model the frequency performance of transistors with Cd 3 As 2 channels, using our experimental measurements of contact resistances, carrier velocities and sheet carrier densities as input parameters.…”

mentioning

confidence: 99%

Prospects of Terahertz Transistors with the Topological Semimetal Cadmium Arsenide

Shoron

Goyal

Guo

et al. 2020

Adv Elect Materials

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Electronic devices that operate at terahertz frequencies will require new materials that exhibit higher carrier velocities than traditional semiconductors. Calculations show that cadmium arsenide, a 3D topological (Dirac) semimetal, is an excellent candidate for field effect transistors that operate at frequencies above 1 THz. Moreover, such transistors have unique advantages that are enabled by the properties of Dirac electrons. These include predictions of an unprecedented linearity of the transconductance and cutoff frequencies over a large operating range and cutoff frequencies that remain above 1 THz at carrier densities as low as 1011 cm−2. The calculations are underpinned by measurements of devices with cadmium arsenide channels. Extremely low contact resistances (<2 × 10−9 Ω cm2), high electron velocities (>7 × 105 m s−1), and unprecedentedly large current densities (up to 10 A mm−1) are demonstrated. Current modulation (>50%) and transconductance already achieved in the early transistors show the potential for large (>10 ×) improvements by reducing interface trap densities. The results demonstrate the significant potential of topological semimetals for high‐speed transistors operating in the THz regime and open up new opportunities for next‐generation RF circuits.

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“…Thus, we infer that the unexpected increase in resistivity after returning to the low pressure regime below P c↓ shown in Figure 2(a) originates in a largely enhanced scattering that outweighs the expected increase in carrier mobilities due to the formation of bulk Dirac points and the gain in the charge carriers from self-doping. We note that studies on Cd 3 As 2 epilayers revealed a substantial effect of extended defects on electron mobilities [52]. Moreover, for epitaxial (112) Cd 3 As 2 films a systematic decrease in Hall mobilities with the compressive in-plane strain ( s 0.4%) was observed [53].…”

Section: Discussionmentioning

confidence: 68%

Pressure-induced reconstructive phase transition in Cd$_3$As$_2$

Gamża,

Abrami,

Gammond

et al. 2020

Preprint

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Cadmium arsenide Cd3As2 hosts massless Dirac electrons in its ambient-conditions tetragonal phase. We report X-ray diffraction and electrical resistivity measurements of Cd3As2 upon cycling pressure beyond the critical pressure of the tetragonal phase and back to ambient conditions. We find that at room temperature the transition between the low-and high-pressure phases results in large microstrain and reduced crystallite size both on rising and falling pressure. This leads to non-reversible electronic properties including self-doping associated with defects and a reduction of the electron mobility by an order of magnitude due to increased scattering. Our study indicates that the structural transformation is sluggish and shows a sizable hysteresis of over 1 GPa. Therefore, we conclude that the transition is first-order reconstructive, with chemical bonds being broken and rearranged in the high-pressure phase. Using the diffraction measurements we demonstrate that annealing at ∼200 °C greatly improves the crystallinity of the high-pressure phase. We show that its Bragg peaks can be indexed as a primitive orthorhombic lattice with aHP ≈ 8.68 Å, bHP ≈ 17.15 Å and cHP ≈ 18.58 Å. The diffraction study indicates that during the structural transformation a new phase with another primitive orthorhombic structure may be also stabilized by deviatoric stress, providing an additional venue for tuning the unconventional electronic states in Cd3As2.

show abstract

Defects in Cd3As2 epilayers via molecular beam epitaxy and strategies for reducing them

Cited by 16 publications

References 25 publications

Pressure-induced reconstructive phase transition inCd3As2

Pressure-induced reconstructive phase transition inCd3As2

Prospects of Terahertz Transistors with the Topological Semimetal Cadmium Arsenide

Pressure-induced reconstructive phase transition in Cd$_3$As$_2$

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