Analysis of the impact of dislocation distribution on the breakdown voltage of GaAs-based power varactor diodes

McNally, Patrick J.; Herbert, P.A.F.; Tuomi, T.; Karilahti, M.; Higgins, J.A.

doi:10.1063/1.362470

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…GaAs, GaP, SiC, CdTe), metals, metallic alloys and dielectric crystals. 19,20 The dislocation rearrangement into cell networks takes place under external or internal stress in the course of plastic relaxation. In growing crystals cellular structures are formed due to the acting of the internal thermomechanical stress field.…”

Section: Discussionmentioning

confidence: 99%

Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

Kirste

Danilewsky

Sochacki

et al. 2015

ECS J. Solid State Sci. Technol.

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The defect structure of HVPE-GaN crystals is examined using synchrotron white-beam X-ray topography (SWXRT) and topography results are interpreted and discussed in comparison to reciprocal lattice point broadening from high resolution X-ray diffraction (HRXRD) measurements. Two as-received commercial HVPE-GaN wafers from two different vendors and one HVPE-GaN which was grown on an ammonothermal GaN-seed are investigated in this study. To our knowledge SWXRT large area back-reflection analysis of HVPE-GaN grown on an ammonothermal GaN seed has been performed for the first time. From large-area topography the formation of a cellular defect network is identified for the commercial HVPE-GaN. Large differences in the crystal lattice misorientation deformation (mosaicity) are determined for the different samples by transmission section topography. For the HVPEGaN grown on an ammonothermal GaN-seed a very low defect density was ascertained. From the contrasts of the topography threading screw-type dislocations and threading mixed-type dislocations were identified. The X-ray topography analysis shows clearly and for the first time that the nature of the defect structure and the low density of ammonothermal GaN seeds can be transferred by HVPE growth of GaN. For demanding GaN-based (opto-)electronic applications such as laser diodes or transistors for high power electronics there is a need for material with low defect densities, since threading dislocations act as centers of non-radiative recombination, increasing the leakage current, reducing the room temperature mobility and so limiting the efficiency, performance and lifetime of devices. Freestanding GaN with low defect density is the substrate material of choice for the realization of such GaN-based device structures with superior properties. Different approaches for crystal growth of bulk GaN like ammonothermal growth, hydride vapor-phase epitaxy (HVPE) and high-and low-pressure solution growth were followed in recent years.1 The ammonothermal growth and HVPE seem to be the most promising methods to produce GaN substrates in sufficient number, size and material quality and substrates prepared with these growth methods have become available commercially in recent years. In the ammonothermal growth method, GaN crystalizes from a solution of Ga in supercritical ammonia with the addition of a mineralizer. For seed material, the ammonothermal growth method uses native GaN crystals. Benefits of the ammonothermal growth method are very low dislocation densities as low as 5 × 10 3 cm −2 and large curvature radii of the crystal planes (>100 m).2 Drawbacks of GaN ammonothermal growth method are the incorporation of impurities and the low growth rate (0.1 mm/day), even when the method can potentially produce hundreds of crystals in a single batch. In comparison, in HVPE the GaN crystallization takes place from the vapor phase by the reaction of ammonia with gallium chloride at temperatures of about 1050• C. HVPE uses GaN seed layers (templates) deposited e.g. by metalorganic v...

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Section: Discussionmentioning

confidence: 99%

Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

Kirste

Danilewsky

Sochacki

et al. 2015

ECS J. Solid State Sci. Technol.

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“…4. McNally et al [7] reported that the breakdown voltage was reduced and scattered due to local field enhancement in the GaAs varacter diodes which were fabricated on dislocated position in the substrate. …”

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confidence: 98%

Influence of dislocation on high-electric-field property in semi-insulating GaAs

Kiyama

Yamada

Tatsumi

2004

13th International Conference on Semiconducting and Insulating Materials, 2004. SIMC-XIII-2004.

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High-electric-field properties such as sub-linear I-V characteristic and low-frequency oscillations (LFOs) have been measured in a low-dislocation-density semi-insulating GaAs crystal. It is found that the sub-linear I-V behaviours and LFO waveforms measured at the cathodes where no dislocations exist are very stable but those measured at the cathodes where several dislocations are observed are not stable but more complicated, which is confirmed from Fourier-transform spectra of LFOs. It is explained that the high-electric-field properties observed here depend on the electrical inhomogeneities induced by the dislocations. IntroductionIt is well known that when the DC electric field over 1 kV/cm is applied to a semi-insulating (SI) GaAs crystal, a sub-linear I-V behaviour is observed and then low-frequency oscillations (LFOs) occur [1]. The LFO phenomena may be understood to occur as a result of field-enhanced capture of electron to EL2 level; that is, the decrease in the free electron concentration due to the field-enhanced capture causes the formation and propagation of a high-electric-field domain. The LFOs cause undesired noises in the actual applications of GaAs FETs [2], and they may be understood as a simple example of nonlinear systems [3]. The sub-linear I-V characteristics, LFO waveforms, and their Fourier-transform spectra (FTS) have been precisely measured by using the three-electrode guard-ring method [4]. It should be noticed that the former experiments [4-6] were made in SI-GaAs crystals with high-dislocation density, because low-dislocation density crystals were not easily available. Therefore, there is no work to investigate the relationship between crystal quality and high-electric-field properties. In the present study, we have investigated the influence of dislocations on these properties with a low-dislocation-density GaAs crystal, which is performed by etching of dislocations in the area of cathode electrode after the I-V, LFO, and FTS measurements. We have found the difference in these properties between at the cathodes where no etch-pit exists and at those where several etch-pits exist are observed. Experimental ProcedureThe experimental setup and the three-electrode guard-ring method employed in the present study are shown in Fig. 1. We can measure precisely, stably, and reproducibly I-V, LFO, and FTS characteristics by using this method, because the electric-field distribution is well controlled and uniform in the sample and the surface leakage current is extremely low and reduced in comparison with the two-electrode method [4].We used a low-dislocation-density (001) GaAs wafer grown by the vertical boat method, whose

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“…dielectric crystals [18,19]. The dislocation rearrangement into cell networks takes place under external or internal stress in the course of plastic relaxation.…”

mentioning

confidence: 99%

(Invited) Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

Kirste

Danilewsky²,

Sochacki

et al. 2015

ECS Trans.

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The defect structure of HVPE-GaN crystals are examined using synchrotron white-beam X-ray topography (SWXRT) and topography results are interpreted and discussed in comparison to reciprocal lattice point broadening from high resolution X-ray diffraction (HRXRD) measurements. Two as-received commercial HVPE-GaN wafers from two different vendors and one HVPE-GaN which was grown on an ammonothermal GaN-seed are investigated in this study. From large-area topography the formation of a cellular defect network is identified for the commercial HVPE-GaN. Large differences in the crystal lattice misorientation deformation (mosaicity) are determined for the different samples by transmission section topography. For the HVPE-GaN grown on an ammonothermal GaN-seed a very low defect density was ascertained. From the contrasts of the topography threading screw-type dislocations and threading mixed-type dislocations were identified. The structure analyses show that the outstanding structural properties of the ammonothermal GaN-seed are adopted by the HVPE-GaN.

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Analysis of the impact of dislocation distribution on the breakdown voltage of GaAs-based power varactor diodes

Cited by 6 publications

References 15 publications

Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

Influence of dislocation on high-electric-field property in semi-insulating GaAs

(Invited) Synchrotron White-Beam X-Ray Topography Analysis of the Defect Structure of HVPE-GaN Substrates

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