Study of residual stress in reactively sputtered epitaxial Si-doped GaN films

Monish, Mohammad; Major, S.S.

doi:10.1016/j.mssp.2022.106902

Cited by 2 publications

(15 citation statements)

References 60 publications

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“…In both cases, the out-of-plane ω−2θ high-resolution scans have shown only (0002), ( 0004) and (0006) reflections of GaN, confirming the formation of single wurtzite phase of GaN, with nearly complete c-axis orientation. The phi (f) scans of (10 11) reflection in both cases [20,42] have confirmed the epitaxial character of the films, conforming to the in-plane relationship of GaN [11 2 0]║α-Al 2 O 3 [10 10] [43] and alignment with the oxygen sub-lattice of sapphire. XPS measurements of undoped GaN films [44] have shown that the N/Ga ratio decreased substantially with decrease of N 2 percentage in sputtering atmosphere.…”

Section: Resultssupporting

confidence: 59%

“…The structural data of undoped [20] and Si-doped [42] GaN films grown at different N 2 percentages in sputtering atmosphere have been reported earlier. In both cases, the out-of-plane ω−2θ high-resolution scans have shown only (0002), ( 0004) and (0006) reflections of GaN, confirming the formation of single wurtzite phase of GaN, with nearly complete c-axis orientation.…”

Section: Resultsmentioning

confidence: 81%

“…These results have thus shown that both undoped and Si-doped epitaxial GaN films grown by sputtering are degenerate, having high carrier concentrations (>10 18 cm −3 ) [34,41]. Our earlier studies [20,42] on the microstructure of undoped and Si-doped GaN films grown epitaxially by sputtering have also shown that these films possess a high density of edge dislocations in the range of 10 11 -10 12 cm −2 . It may be mentioned here, that in spite of the recent progresses in the growth of epitaxial GaN films by sputtering and promising device applications [30], studies related to their electronic properties and dependence on microstructure and defects remain rather limited, compared to the enormous scientific literature that exists on MBE and MOCVD grown GaN.…”

Section: Introductionmentioning

confidence: 71%

“…Undoped and Si-doped GaN epitaxial films were grown on c-sapphire substrate respectively by reactive sputtering of GaAs (3-inch diameter) and GaAs-Si composite target, using an approach similar to that used in our earlier work [20,42]. For the in situ incorporation of Si, the erosion track of GaAs was partially covered by Si and the Si area coverage of the erosion track of GaAs was fixed at ∼5%, based on earlier studies, which indicated the deterioration of the structural quality of films grown with larger area coverages [23].…”

Section: Methodsmentioning

confidence: 99%

“…ESCApe software was used for the analysis of core level spectra, which were fitted with Shirley-type background and a combination of Gaussian and Lorentzian line shape components for the peak envelope. High resolution x-ray diffraction (HRXRD) measurements were carried out with a Cu rotating anode (9 kW), RIGAKU-Smart Lab-x-ray diffractometer, equipped with a 2-bounce Ge (220) monochromator, to calculate the density of edge dislocations from mosaic twist, obtained by in-plane measurements of (11 ̅ 20) reflection, as described elsewhere [20,42].…”

Section: Methodsmentioning

confidence: 99%

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Electrical transport in epitaxially grown undoped and Si-doped degenerate GaN films

Monish,

Major

2024

Phys. Scr.

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This study investigates the electrical transport properties of undoped and Si-doped, degenerate GaN heteroepitaxial films grown on sapphire by reactive rf sputtering of GaAs (and Si) in Ar-N2 mixture. The room temperature electrical measurements showed that the resistivity of undoped GaN film grown at 100% N2 was ~2 × 105 Ω cm, which reduced to ~1 Ω cm in Si-doped film, revealing the effect of Si doping. With decrease of N2 from 100% to 75%, the carrier concentration of Si-doped films increased from ~7 × 1018 cm-3 to ~2 × 1019 cm-3, but remained practically unchanged as N2 was decreased to 20%, which is explained by effects due to saturation of Si doping and increase of Ga interstitials as well as compensation by N interstitials and Ga vacancies. Undoped and Si-doped films grown below 20% N2 displayed similar carrier concentrations (~1020 cm-3), due to dominance of Ga interstitials. Both undoped and Si-doped films were degenerate and displayed increase of mobility with carrier concentration and temperature, which was analyzed by the combined effect of ionized impurity and dislocation scattering, using compensation ratio as fitting parameter. At carrier concentrations ≲1019 cm-3, the mobility was governed by both ionized impurity and dislocation scattering, while at higher carrier concentrations, ionized impurity scattering was found to dominate, limited by compensation due to acceptors. In spite of the degenerate character, the films displayed a small decrease of carrier concentration with temperature, along with a nearly linear decrease of mobility, which are explained by a marginal increase of compensation ratio with decrease of temperature, taking into account the band edge fluctuation effects. These features of electrical transport have not been much explored for heteroepitaxial, n-type degenerate GaN films, possessing high density of dislocations and point defects.

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Section: Resultssupporting

confidence: 59%

Section: Resultsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 71%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Electrical transport in epitaxially grown undoped and Si-doped degenerate GaN films

Monish,

Major

2024

Phys. Scr.

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Mg incorporation induced microstructural evolution of reactively sputtered GaN epitaxial films to Mg-doped GaN nanorods

Monish,

Major

2024

Nanotechnology

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Mg-doped GaN films/nanorods were grown epitaxially on c-sapphire by reactive co-sputtering of GaAs and Mg at different N2 percentages in Ar-N2 sputtering atmosphere. Energy dispersive x-ray spectroscopy revealed that the Mg incorporation increases with increase of Mg area coverage of GaAs target, but does not depend on N2 percentage. In comparison to undoped GaN films, Mg-doped GaN displayed substantial decrease of lateral conductivity and electron concentration with the initial incorporation of Mg, indicating p-type doping, but revealed insulating behaviour at larger Mg content. Morphological investigations by scanning electron microscopy have shown that the films grown with 2% - 4% Mg area coverages displayed substantially improved columnar structure, compared to undoped GaN films, along with rough and voided surface features at lower N2 percentages. With increase of Mg area coverage to 6%, the growth of vertically aligned and well-separated nanorods, terminating with smooth hexagonal faces was observed in the range of 50% - 75% N2 in sputtering atmosphere. High-resolution x-ray diffraction studies confirmed the epitaxial character of Mg-doped GaN films and nanorods, which displayed complete c-axis orientation of crystallites and a mosaic structure, aligned laterally with the c-sapphire lattice. The catalyst-free growth of self-assembled Mg-doped GaN nanorods is attributed to increase of surface energy anisotropy due to the incorporation of Mg. However, with further increase of Mg area coverage to 8%, the nanorods revealed lateral merger, suggesting enhanced radial growth at larger Mg content.

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Study of residual stress in reactively sputtered epitaxial Si-doped GaN films

Cited by 2 publications

References 60 publications

Electrical transport in epitaxially grown undoped and Si-doped degenerate GaN films

Electrical transport in epitaxially grown undoped and Si-doped degenerate GaN films

Mg incorporation induced microstructural evolution of reactively sputtered GaN epitaxial films to Mg-doped GaN nanorods

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