Study of Thin films Polarity of Group III Nitrides

Dovidenko, K.; Oktyabrsky, S.; Narayan, J.; Razeghi, Manijeh

doi:10.1557/s109257830000332x

Cited by 8 publications

(7 citation statements)

References 12 publications

(19 reference statements)

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“…The smooth films grown under optimum or nitrogen-rich conditions by MOCVD and at optimum temperature by PLD have shown Ga-face (0001) polarity [11]. The same Ga-polarity has been found for the wurtzite grains with c-axis normal to the substrate surface as shown in the left inset of the Fig.…”

Section: Disscusionsupporting

confidence: 68%

“…4, the hexagonal grains with c-axis normal to the substrate surface and those with the inclined c-axis would have opposite face polarity, if the latter grains are nucleated on the cubic phase faces and the polarity is preserved across the phase interface. We have used CBED to determine the polarity of the grains [11]. Due to dynamic electron beam scattering by the non-centrosymmetric specimen, the CBED pattern loses the inversion symmetry.…”

Section: Disscusionmentioning

confidence: 99%

“…Due to dynamic electron beam scattering by the non-centrosymmetric specimen, the CBED pattern loses the inversion symmetry. Unlike a common method involving simulation of the CBED contarst for quite thick specimen regions [12,13], we have proposed a technique based on the study of the thinnest (< 150 Å) regions of the wurtzite grains [11]. The simulaton of the CBED as well as pendellössung curves (beam intensity vs. thickness) shows that the pattern from a very thin regions carries unambiguous information about polarity as can be seen in the inserts of the Fig.…”

Section: Disscusionmentioning

confidence: 99%

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CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

Oktyabrsky¹,

Dovidenko²,

Sharma³

et al. 1999

MRS Internet j. nitride semicond. res.

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We have studied crystal structure and associated defects in GaN films grown on sapphire under nitrogen-deficient conditions by metalorganic chemical vapor deposition (MOCVD) and pulsed laser deposition (PLD). The structural quality of the PLD films grown at 750 0 C was comparable with those grown by MOCVD at 1050 0 C having threading dislocations density of about 10 10 cm -2 at a film thickness 150-200 nm. Microstructure of the PLD films grown at temperatures above 780 0 C was found to be similar to that of nitrogen-deficient MOCVD films indicating the loss of nitrogen due to thermal decomposition of the nitride layers. Nitrogen-deficient MOCVD and PLD films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. Most of the stoichiometric films displayed (0001) Ga-face polarity, but the renucleated inclined wurtzite grains grew in the opposite N-face polarity. The major defects related to the cubic structural metastability are stacking faults and microtwins which being nuclei of the metastable cubic phase have an extremely low energy. We elucidate that the cubic phase is more stable under the nitrogen deficiency and, therefore, can exist without decomposition at higher nitrogen vacancy concentrations in the material.

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Section: Disscusionsupporting

confidence: 68%

Section: Disscusionmentioning

confidence: 99%

Section: Disscusionmentioning

confidence: 99%

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CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

Oktyabrsky¹,

Dovidenko²,

Sharma³

et al. 1999

MRS Internet j. nitride semicond. res.

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“…In MOVPE, usually Ga-polar (+c polar) GaN has been epitaxially grown with smooth surfaces. Device quality films grown by MOVPE have been reported to have Ga-polarity [1]. On the other hand, N-polar (-c polar) GaN has been reported to have rough surfaces [2,3].…”

Section: Introductionmentioning

confidence: 99%

N‐polarity GaN on sapphire substrate grown by MOVPE

Matsuoka¹,

Kobayashi²,

Takahata³

et al. 2006

Physica Status Solidi (b)

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15.Kk N-polar GaN was grown on (0001) sapphire using two-step growth technique by MOVPE. In the growth, the key points were the controlling of the density of nuclei in a buffer layer and promoting lateral growth at high temperature. The grown GaN films had mirror-like smooth surfaces and were proved to have N-polarity using convergent-beam electron diffraction and coaxial impact-collision ion spectroscopy. The FWHM of this GaN in the ω-scan was also much narrower than the previous reports. The density of threading dislocations was much less than for usual Ga-polar GaN grown with a GaN or AlN buffer layer by MOVPE and MBE. In PL at room temperature, the strong edge emission was observed as Ga-polarity. The p-type conduction in Mg-doped GaN was also realized by the same methods as for Ga-polarity.

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“…The origin of the open cores in epitaxial polar materials can be correlated to the nucleation stage or to the impurities incorporated during the growth stage. The occurrence of inversion domains (IDs) in unintentionally doped GaN layers is often observed in MOVPE [9]. In addition, it has been reported that an excess amount of Mg causes IDs in GaN films [10].…”

mentioning

confidence: 99%

Growth of highly resistive Ga‐polar GaN by LP‐MOVPE

Mita

Collazo

Dalmau

et al. 2007

Phys. Status Solidi (c)

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Electrical characteristics of 1.3 µm thick GaN films were investigated with respect to the polar type. Unintentionally doped N-polar GaN grown on nitrided sapphire substrates had a hexagonal facetted morphology and consistently exhibited a high n-type conductivity with a sheet resistance of ~10 Ω/sq, corresponding to a carrier concentration on the order of 10 19 cm -3 . In contrast, Ga-polar GaN films grown on low temperature AlN buffer layers showed a high sheet resistance of ~109 Ω/sq. GaN films of mixed polarity exhibited sheet resistance in-between the two extreme values obtained for polarity pure films. The results of this work show that the existence of N-polar domains (even on the nano-scale) in an otherwise Ga-polar matrix significantly decreases the insulating properties of unintentionally doped GaN films.

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Study of Thin films Polarity of Group III Nitrides

Cited by 8 publications

References 12 publications

CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

CRYSTAL STRUCTURE AND DEFECTS IN NITROGEN-DEFICIENT GaN

N‐polarity GaN on sapphire substrate grown by MOVPE

Growth of highly resistive Ga‐polar GaN by LP‐MOVPE

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