Minority carrier diffusion length in GaN: Dislocation density and doping concentration dependence

Kumakura, Kazuhide; Makimōto, Toshiki; Kobayashi, Naoki; Hashizume, Tamotsu; Fukui, Takashi; Hasegawa, Hideki

doi:10.1063/1.1861116

Cited by 216 publications

(112 citation statements)

References 18 publications

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“…And electrons are considered as major carriers because of much lower hole than electron mobility in n-type GaN. [ 18 ] Infl uence of holes and patterned holes on the measurements are described in the Supporting Information. Figure 3 (b) summarizes the measured sheet carrier density (black squares) and mobilities (red dots) as a function of excitation power.…”

Section: Uv-assisted Hall Measurementmentioning

confidence: 99%

Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor

Xiong

Park

Song

et al. 2014

Adv Funct Materials

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We report in this work the fabrication of single crystal GaN nanomembranes, with a thickness as low as 50 nm. Large area (≥5 mm × 5 mm) GaN membranes are produced by electrochemical etching (ECE) with a special high-conductivity sacrifi cial underlayer. Large-area, crackfree transfer of GaN NMs have been performed onto metal, glass, and polymer target substrates. The transport properties of freestanding GaN nanomembranes are analyzed using UV-assisted Hall measurements. The interaction of the carriers with the surface electronic states are investigated by the intensity dependence of the photoconductor gain, and by the temperature-dependent measurements of photocurrent decay. The transport property of GaN NM, down to a thickness of 90 nm, remains very comparable to that from much thicker GaN structures. Enhancement-mode fi eld effect transistors (FETs) have been fabricated and demonstrated on a SiO 2 / Si(001) wafer, suggesting that GaN nanomembranes can be a new candidate for fl exible electronics requiring high power and high-frequency. Results and Discussion Nanomembrane FabricationThe principle of using an ECE process to selectively remove underlying GaN sacrifi cial layers has been described before. [ 12,13 ] Multi-layered GaN structures having nanomembrane layers (50 to 500 nm thick) on top of heavily-doped ( n ≈ 1 × 10 19 cm −3 ) GaN sacrifi cial layers were grown by metal-organic chemical vapor deposition (MOCVD) process on sapphire. To obtain large-area NM within a reasonable time, a periodic array of via holes were created such that the undercut etching can proceeds uniformly around these openings. The via-holes are squares with a dimension of 10 µm and a diagonal periodicity of 25, 50, and 100 µm. These holes were created by Cl-based inductively coupled plasma (ICP) etching to expose the sacrifi cial layer. The photoresist (Shipley S1827) used during the Cl-ICP etching was retained to protect the front surface of the membrane during ECE. The nanomembrane layers became detached from the substrate once the undercut regions around each opening coalesce with the adjacent ones. GaN NMs were cleaned by rinsing sequentially in DI water, acetone and isopropyl-alcohol (IPA). After cleaning, they were transferred on to other substrates Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor Kanglin Xiong , Sung Hyun Park , Jie Song , Ge Yuan , Danti Chen , Benjamin Leung , and Jung Han * Large-area, free-standing and single-crystalline GaN nanomembranes are prepared by electrochemical etching from epitaxial layers. As-prepared nanomembranes are highly resistive but can become electronically active upon optical excitation, with an excellent electron mobility. The interaction of excited carriers with surface states is investigated by intensity-dependent photoconductivity gain and temperature-dependent photocurrent decay. Normally off enhancement-type GaN nanomembrane MOS transistors are demonstrated, suggesting that GaN could be used in fl exible electronics for high power and hig...

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Section: Uv-assisted Hall Measurementmentioning

confidence: 99%

Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor

Xiong

Park

Song

et al. 2014

Adv Funct Materials

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“…Notably, both CL and electron beam induced current studies [49] place an upper limit to the minority carrier diffusion lengths in GaN in the 50-250 nm range -significantly lower than the micron scale and longer diffusions lengths found for other III-Vs. These short diffusion lengths are consistent with an increased tolerance to high defect densities [88] and suggest that alternative mechanisms, not interactions with TDs, limit carrier diffusion lengths.…”

Section: Extended Defectsmentioning

confidence: 99%

Research challenges to ultra‐efficient inorganic solid‐state lighting

Phillips¹,

Coltrin

Crawford

et al. 2007

Laser & Photonics Reviews

378

268

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Solid-state lighting is a rapidly evolving, emerging technology whose efficiency of conversion of electricity to visible white light is likely to approach 50% within the next several years. This efficiency is significantly higher than that of traditional lighting technologies, giving solid-state lighting the potential to enable significant reduction in the rate of world energy consumption. Further, there is no fundamental physical reason why efficiencies well beyond 50% could not be achieved, which could enable even more significant reduction in world energy usage. In this article, we discuss in some detail: (a) the several approaches to inorganic solid-state lighting that could conceivably achieve "ultra-high," 70% or greater, efficiency, and (b) the significant research questions and challenges that would need to be addressed if one or more of these approaches were to be realized.

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“…Measured diffusion lengths values are in line with reported values (L p = 23 nm, L n ≈ 30 nm) in literature for cross-sectional EBIC in planar GaN p−n junctions at low ebeam energy (1 keV) 46 but larger values (L p = 80−950 nm, L n = 70−250 nm) were reported in studies with larger ebeam energies (5, 10 keV). 49,50 EBIC signal was also recorded as a function of applied voltage U. During a single image acquisition (∼500 nm along the junction), reverse bias was varied by step of 1 V from 0 to −3 V. The four curves are reported in Figure 1b.…”

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confidence: 99%

Direct Imaging of p–n Junction in Core–Shell GaN Wires

et al. 2014

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While core−shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor properties along the threedimensional (3D) buried p−n junction. Thanks to a crosssectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core−shell wire p−n junctions grown by catalyst-free metal−organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40−50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor N a and donor N d doping levels were locally determined to be N a = 3 × 10 18 cm −3 and N d = 3.5 × 10 18 cm −3 in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core−shell wire devices.

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Minority carrier diffusion length in GaN: Dislocation density and doping concentration dependence

Cited by 216 publications

References 18 publications

Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor

Single Crystal Gallium Nitride Nanomembrane Photoconductor and Field Effect Transistor

Research challenges to ultra‐efficient inorganic solid‐state lighting

Direct Imaging of p–n Junction in Core–Shell GaN Wires

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