Mobility in epitaxial GaN: Limitations of free-electron concentration due to dislocations and compensation

Gurusinghe, Manjula; Andersson, T. G.

doi:10.1103/physrevb.67.235208

Cited by 48 publications

(35 citation statements)

References 44 publications

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“…Their electronic states interact with the free electrons. 17 We consider the effect of them on the 2DEG concentration to be limited. In the Measurements section, we accounted for 2DEG densities as high as 2.8 ϫ 10 13 cm Ϫ2 with x Al ϭ 0.40 and t AlGaN ϭ 400 Å.…”

Section: Discussionmentioning

confidence: 99%

The influence of composition and unintentional doping on the two-dimensional electron gas density in AlGaN/GaN heterostructures

Davidsson

Gurusinghe

Andersson

et al. 2004

Journal of Elec Materi

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We have studied the influence of Al content, AlGaN layer thickness, and unintentional background doping by oxygen on the two-dimensional electron gas (2DEG) density in AlGaN/GaN heterostructures. Hall measurements were made on samples grown with molecular beam epitaxy. The 2DEG densities in the range 2-3 ϫ 10 13 cm Ϫ2 were measured. A one-dimensional Schrödinger-Poisson model was used to describe the heterostructure. The calculations gave twodimensional electron densities in accordance with measured values. The electron density is very sensitive to the Al concentration in the AlGaN layer, whereas the sensitivity to layer thickness is small. Our simulations also showed that the two-dimensional concentration increased 50% when the free-carrier concentration changed from 10 15 cm Ϫ3 to 10 18 cm Ϫ3 . The relation between donor concentration and free-carrier concentration was found to agree when using oxygen ionization energy as a parameter.

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Section: Discussionmentioning

confidence: 99%

The influence of composition and unintentional doping on the two-dimensional electron gas density in AlGaN/GaN heterostructures

Davidsson

Gurusinghe

Andersson

et al. 2004

Journal of Elec Materi

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“…As for the electrical properties, temperature dependence of electron mobilities was shown in Fig. 2 [18], indicating that reduction of impurity, dislocations and compensations [19,20] should be done by optimizing growth condition such as insertion of ZnO/MgO layers [19] or precise control of Zn/O flux ratio [21]. In comparison with that of high quality epitaxial ZnO layers, electron mobility and concentration at RT are still inferior than 158 cm 2 /Vs and 2.2 × 10 16 cm -3 in homoepitaxial layer but close to 130 cm 2 /Vs 1.2 × 10 17 cm -3 in heteroepitaxial one [22].…”

mentioning

confidence: 96%

Characterization of undoped ZnO layers grown by molecular beam epitaxy towards biosensing devices

Ogata¹,

Komuro²,

Hama³

et al. 2004

Physica Status Solidi (b)

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Undoped ZnO layers grown by molecular beam epitaxy (MBE) were investigated aiming at biosensing devices based on organic/inorganic hybrid structures. Clear observation of free exciton emission in low temperature photoluminescence (PL) spectra and electron mobility as high as 114 cm 2 /Vs at room temperature indicate that the quality of the ZnO layers is applicable for biosensors. Surface bonding of the ZnO the layers, which is one of the key issues for hybridization, was examined by means of xray photoelectron spectroscopy (XPS). The XPS spectra of O 1s revealed that formation and desorption of hydroxyl (OH) bonds can be controlled by air exposure and thermal treatments. , establishment of hybridization between biofunctionalized molecules and inorganic semiconductor systems is of high importance. Until now, Si-based FETs are mainly utilized for them, however, compound semiconductors should be another candidates. In termes of fabrication of hybridized structures, their controllability of bandgap energies and lattice constants, which resulted in realization of laser diodes and high electron mobility transistors (HEMTs), would possess several potential. Among lots of compounds, i.e., numerous combinations of elements, we have chosen zinc oxide (ZnO) based semiconductors as materials for EnFET and biochemical sensors from the following reasons.One of the advantages of ZnO is expected to easily form direct bonding between organic molecules and the oxide surface. In case of non-oxide compounds, surface cleaning is necessary for precise bonding control, which can be realized by the removal of unintentionally formed amorphous oxide layer at the surface, while oxide surfaces are free from that. Considering that direct binding of biofunctional molecules on insulating gate layers in FETs is preferable for signal processing, availability of crystalline insulating layers of oxides is crucial for hybridization. Also it is expected that the techniques of selfassembled monolayer formation using organothiols on gold [3] would be applicable on oxide surfaces by the reaction between cation in oxide and S in molecules. In addition, multi-functionality of ZnO, such as large bandgap energy of 3.3eV for transparent electronics [4] and piezoelectricity for actuator [5], would be interesting for hybridization devices. From the viewpoint of biomedical applications, less hazardousness of oxides has attracted a great deal of attention, where other compound semiconductors cannot work.Recent progress on epitaxial growth of ZnO based semiconductors has been performed by molecular beam epitaxy (MBE) [6,7], pulsed laser deposition (PLD) [8,9] and metalorganic vapor phase epitaxy

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“…To describe the PL emission we use a model by Gurusinghe et al [11], where dislocation lines are treated as negatively charged, due to acceptor-like states along their length. A positive space-charge region, with radius R, will be formed around each dislocation to compensate for the negative charge, where R depends strongly on the bulk carrier concentration.…”

Section: Methodsmentioning

confidence: 99%

“…Due to the high efficiency of high dislocation nitride materials, further investigation is desired to increase our understanding. In this work, we have expanded the model of Gurusinghe et al [11] to predict PL intensity of GaN and compared the model to experimental results.…”

Section: Introductionmentioning

confidence: 97%

“…In another approach, the mobility was calculated due to scattering of electrons at filled traps along dislocation lines [10]. Further, a detailed numerical description of the free electron concentration and mobility due to charged dislocation lines has been made [11]. Due to the high efficiency of high dislocation nitride materials, further investigation is desired to increase our understanding.…”

Section: Introductionmentioning

confidence: 99%

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Influence of dislocation density on photoluminescence intensity of GaN

Fälth

Gurusinghe

et al. 2005

Journal of Crystal Growth

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Mobility in epitaxial GaN: Limitations of free-electron concentration due to dislocations and compensation

Cited by 48 publications

References 44 publications

The influence of composition and unintentional doping on the two-dimensional electron gas density in AlGaN/GaN heterostructures

The influence of composition and unintentional doping on the two-dimensional electron gas density in AlGaN/GaN heterostructures

Characterization of undoped ZnO layers grown by molecular beam epitaxy towards biosensing devices

Influence of dislocation density on photoluminescence intensity of GaN

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