Hexacoordinated Gallium(III) Triazenide Precursor for Epitaxial Gallium Nitride by Atomic Layer Deposition

Abstract

Gallium nitride (GaN) is the main component of modern-day high electron mobility transistor electronic devices due to its favorable electronic properties. As electronic devices become smaller with more complex architecture, the ability to deposit high-quality GaN films at low temperature is required. Herein, we report a new highly volatile Ga(III) triazenide precursor and demonstrate its ability to deposit high-quality epitaxial GaN by atomic layer deposition (ALD). This new Ga(III) triazenide precursor, the first hexacoordinated M–N bonded Ga(III) precursor used in a vapor deposition process, was easily synthesized and purified by sublimation. Thermogravimetric analysis showed single step volatilization with an onset temperature of 150 °C and negligible residual mass. Three temperature intervals with self-limiting growth were observed when depositing GaN films. In the second growth interval, the films were found to be near stoichiometric with very low levels of impurities and epitaxial orientation on 4H-SiC without an AlN seed layer. The films grown at 350 °C were found to be smooth with a sharp interface between the substrate and film. The bandgap of these films was 3.41 eV with the Fermi level at 1.90 eV, showing that the GaN films were unintentionally <i>n</i>-type doped. This new triazenide precursor enables ALD of GaN for semiconductor applications and provides a new Ga(III) precursor for future deposition processes.

Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition

“…In previous work, we demonstrated high-quality thin films of indium nitride and gallium nitride by ALD, using the Ga(triaz) 3 and In(triaz) 3 as precursors, respectively. 32 , 31 From the thermal properties of the compounds, we speculated that the depositions are activated by gas-phase decomposition of the precursor in the ALD reactor. Compounds 1 – 6 have similar thermal properties as Ga(triaz) 3 and In(triaz) 3 and are therefore expected to undergo a similar decomposition.…”

“…Homoleptic hexacoordinated Al(III) triazenide complexes have previously been reported; 29 , 30 however, they are not volatile due to their 1,3-diphenyltriazenide ligands. Recently, we reported the first examples of highly volatile homoleptic 1,3-dialkyltriazenide complexes, tris(1,3-diisopropyltriazenide)In(III) (In(triaz) 3 ) 31 and Ga(III) (Ga(triaz) 3 ), 32 and their use as ALD precursors. These new triazenide precursors underwent gas-phase decomposition at higher temperatures inside the ALD reactor, giving a smaller and more reactive M(III) species.…”

In0.5Ga0.5N Layers by Atomic Layer Deposition

“…In summary, we have developed a new ALD approach for ternary materials based on co-sublimation of the metal precursors as an alternative to the super-cycle approach. This method was employed 1,7x10 14 3,3x10 14 6,7x10 14 8,3x10 14 5,0x10 14 1,0x10 15 (ahv)^2(eV cm -1 )…”

“…We have previously investigated ALD of InN and GaN using tris(1,3diisopropyltriazenide)indium(III) 12 (1) and gallium(III) 14 (2) (Fig. S1), rendering stable ALD behavior with self-limiting deposition, wide temperature ranges where the growth per cycle is not affected by the temperature and a high growth per cycle, combined with good structural and electronic properties of the materials.…”

“…Growth of epitaxial In1-xGaxN was attempted on 4H-SiC (0001) as it is a suited substrate for both epitaxial InN and GaN. 12,14 When depositing In1-xGaxN directly on 4H-SiC, without a nucleation layer, using a 1:1 (In:Ga) precursor mix, sublimation temperature 130 °C and deposition temperature 350 °C, In1-xGaxN was obtained. In the -2 XRD measurement (Fig.…”