Relationship between physical properties and gas purification in GaN grown by metalorganic vapor phase epitaxy

The full performance of GaN devices for high-power applications is not exploited due to the selfheating. Possible solutions are the integration of materials with high heat conductivity i.e., single crystalline diamond and graphene layers. We report the growth of single crystalline (0001)-oriented GaN thin film on (100), (110) and (111) diamond single crystals studied by transmission electron microscopy (TEM) in cross-sections. As for graphene, we show a high-quality GaN layer that was deposited on patterned graphene layers and 6H-SiC. The atomic structures of the interfaces in the heterostructure are studied using aberration-corrected scanning TEM combined with energy dispersive X-ray and electron energy-loss spectroscopy.

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“…Similar effect was observed, when low amount of carbon was introduced into carbon-indium co-doped GaAs grown by MOCVD [17].…”

Section: Gan Grown On Patterned Graphenesupporting

confidence: 78%

GaN heterostructures with diamond and graphene

Pécz

Tóth

Tsiakatouras

et al. 2015

Semicond. Sci. Technol.

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“…For GaN, n-type conductivity is easily obtained by substituting, Ga with Si (Si Ga ) [67], Ge (Ge Ga ) [67] or Se (Se Ga ) [92] or substituting N with O (O N ) [93]. All these donors are found to form shallow, hydrogen-like, donors with low activation energy in the range of ~30 meV which is in good agreement with effective mass theory.…”

Section: Si Doping Of Algansupporting

confidence: 73%

Doping of high-Al-content AlGaN grown by MOCVD

Nilsson¹

2014

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The high-Al-content Al x Ga 1-x N, x > 0.70, is the principal wide-band-gap alloy system to enable the development of light-emitting diodes operating at the short wavelengths in the deep-ultraviolet, λ < 280 nm. The development of the deep-ultraviolet light-emitting diodes (DUV LEDs) is driven by the social and market impact expected from their implementation in portable units for water/surface disinfection and based on the damaging effect of the deep-ultraviolet radiation on the DNA of various microorganisms. Internationally, intense research and technology developments occur in the past few years, yet, the external quantum efficiency of the DUV LEDs is typically below 1%.One of the main material issues in the development of the DUV LEDs is the achievement of n-and ptype high-Al-content Al x Ga 1-x N layers with low resistivity, which is required for the electrical pumping of the diodes. The doping process becomes significantly more complex with increasing the Al content and the electrical resistivity is as high as 10 1 -10 2 Ω . cm for n-type AlN doped by silicon, and 10 7 -10 8 Ω cm for p-type AlN doped by magnesium.The present study was therefore focused on gaining a better understanding of the constraints in the doping process of the high-Al-content Al x Ga 1-x N alloys, involving mainly silicon. For this purpose, the epitaxial growth of the high-Al-content Al x Ga 1-x N and AlN by implementing the distinct hot-wall MOCVD was developed in order to achieve layers of good structural and morphological properties, and with low content of residual impurities, particularly oxygen and carbon. Substitutional point defects O N and C N may have a profound impact on the doping by their involvement in effects of ntype carrier compensation. The process temperature was varied between 1000 and up to 1400 °C, which is a principal advantage in order to optimize the material properties of the high-Al-content Al x Ga 1-x N and AlN. The epitaxial growth of the high-Al-content Al x Ga 1-x N and AlN was largely performed on 4H-SiC substrates motivated by (i) the lattice mismatch of ~ 1% along the basal plane (the smallest among other available substrates including Si and sapphire), (ii) the good thermal conductivity of 3.7 W cm -1 K -1 , which is essential to minimize the self-heating during the operation of any light-emitting diode, and (iii) the limited access to true-bulk AlN wafers. The outcome of this study is accordingly summarized and presents our understanding for (i) the complex impact of silicon and oxygen on the n-type conductivity of Al 0.77 Ga 0.23 N, representative for the alloy composition at which a drastic reduction of the n-type conductivity of Al x Ga 1-x N is commonly reported (paper 1); (ii) the strain and morphology compliance during the intentional iv doping by silicon and magnesium, and its correlation with the resistivity of highly doped layers of Al 0.82 Ga 0.18 N alloy composition (paper2); (iii) the n-type conductivity of highly Si-doped Al 0.72 Ga 0.28 N as bound by the process temperature (p...

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“…The decomposition pathway from C1 to the most stable intermediate (CH 3 calculated by Ahlrichs-VTZP is about 6.0 kcal/mol higher than that calculated by 6-31G(d,p) basis set. The final step for the formation of GaN from the decomposition of CH 3 GaNH require 47.4 kcal/mol of endothermic energy calculated at CCSD(T)//MP2 level of theory whereas the product system is 69.6 kcal/mol above the initial reactants at the same level of theory.…”

Section: Table 2: Relative Energies a (Kcal/mol) Of Species Involved mentioning

confidence: 65%

“…30,31 The enthalpy values are corrected for the internal rotation present in the molecules for the methyl group. For this purpose, the rotational PES is scanned using PM3 semiempirical method and the rotation barrier height is calculated on the basis of (CH 3 ) 3 …”

Section: Computational Detailsmentioning

confidence: 99%

“…The initial association of TMG with ammonia results in formation of a pre-equilibrium charge transfer complex (CH 3 ) 3 Ga:NH 3 C1 where the electron deficient Ga(CH 3 ) 3 and the donor NH 3 maintain a nonbonded distance of 2.204 Å. The experimental Ga-C bond-length 1.967 Å in (CH 3 ) 3 Ga is close to our calculated theoretical values, but the experimental Ga-N length 2.161 Å as well as Ga-C length 1.979 Å in (CH 3 ) 3 Ga: NH 3 is little away from our calculated values. 38,39 The formation of the complex C1 is completely barrier free, and the lowering of energy due to the complexation is calculated to be 18.8 kcal/ mol at both CCSD(T)//B3LYP/[LANL2DZ-ECP + 6-31G(d,p)] and CCSD(T)//MP2/[LANL2DZ-ECP + 6-31G(d,p)] level of theories.…”

Section: Table 2: Relative Energies a (Kcal/mol) Of Species Involved mentioning

confidence: 99%

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Computational Study on the Growth of Gallium Nitride and a Possible Source of Oxygen Impurity

et al. 2010

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The reaction pathways for the gallium nitride GaN growth by gas phase reaction of trimethylgallium (TMG) with ammonia is studied theoretically. Water is the most important impurity in ammonia, therefore its reaction with TMG is investigated as a possible source of oxygen impurity in GaN. Gallium oxide (GaO) formed by the reaction between TMG and H(2)O is predicted to be one of the possible source of oxygen impurity in GaN. The mechanisms and energetics of these reactions in the gas phase have been investigated by density functional B3LYP/[LANL2DZ-ECP + 6-31G(d,p)] method and ab initio MP2/[LANL2DZ-ECP + 6-31G(d,p)], CCSD(T)/[LANL2DZ-ECP + 6-31G(d,p)]//B3LYP/[LANL2DZ-ECP + 6-31G(d,p)], CCSD(T)/[LANL2DZ-ECP + 6-31G(d,p)]//MP2/[LANL2DZ-ECP + 6-31G(d,p)], and CCSD(T)/[LANL2DZ-ECP + Ahlrichs-VTZP]//MP2/[LANL2DZ-ECP + Ahlrichs-VTZP] methods. Both the reactions of TMG with NH(3) and H(2)O are modeled using pre-equilibrium charge-transfer complexes (CH(3))(3)Ga:NH(3) (C1) and (CH(3))(3)Ga:OH(2) (C2) having binding energies of 18.8 and 12.4 kcal/mol, respectively. The first step of the methane elimination reaction from the complexes proceeds through the saddle points TS1 and TS1a having activation barriers 37.0 and 22.6 kcal/mol for C1 and C2, respectively. The first CH(4) elimination step is exothermic for both the cases, but the exothermicity is 15.0 kcal/mol greater for CH(4) elimination from C2. The next step of methane elimination from the stable reaction intermediates (CH(3))(2)GaNH(2) and (CH(3))(3)GaOH has a very high activation barrier of 76.0 and 67.8 kcal/mol via saddle points TS2 and TS2a, respectively. The calculated reaction rates at 298.15 K for both the reactions are low but are comparable to each other. The total rate constant k(tot) for GaN formation is 2.07 x 10(-60) cm(3) molecule(-1) s(-1), and that for GaO formation is 6.85 x 10(-62) cm(3) molecule(-1) s(-1).

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Relationship between physical properties and gas purification in GaN grown by metalorganic vapor phase epitaxy

Cited by 27 publications

References 1 publication

GaN heterostructures with diamond and graphene

GaN heterostructures with diamond and graphene

Doping of high-Al-content AlGaN grown by MOCVD

Computational Study on the Growth of Gallium Nitride and a Possible Source of Oxygen Impurity

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