DFT Study of Initial Surface Reactions in Gallium Nitride Atomic Layer Deposition Using Trimethylgallium and Ammonia
The initial surface reaction of gallium nitride (GaN) grown by atomic layer deposition (GaN-ALD) was investigated using density functional theory (DFT) calculations. Trimethylgallium (TMG) and ammonia (NH<sub>3</sub>) were used as gallium (Ga) and nitrogen (N) precursors, respectively. D...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Applied Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3417/15/13/7487 |
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| Summary: | The initial surface reaction of gallium nitride (GaN) grown by atomic layer deposition (GaN-ALD) was investigated using density functional theory (DFT) calculations. Trimethylgallium (TMG) and ammonia (NH<sub>3</sub>) were used as gallium (Ga) and nitrogen (N) precursors, respectively. DFT calculations at the B3LYP/6-311+G(2d,p) and 6-31G(d) levels were performed to compute relative energies and optimize chemical structures, respectively. TMG adsorption on Si<sub>15</sub>H<sub>18</sub>–(NH<sub>2</sub>)<sub>2</sub> and Si<sub>15</sub>H<sub>20</sub>=(NH)<sub>2</sub> clusters was modeled, where –NH<sub>2</sub> and =NH surface species served as adsorption sites. The reaction mechanisms in the adsorption and nitridation steps were investigated. The results showed that TMG can adsorb on both surface adsorption sites. In the initial adsorption stage, TMG adsorbs onto =NH- and –NH<sub>2</sub>-terminated Si(100) surfaces with activation energies of 1.11 and 2.00 eV, respectively, indicating that the =NH site is more reactive. During subsequent NH3 adsorption, NH<sub>3</sub> adsorbs onto the residual TMG on the =NH- and –NH<sub>2</sub>-terminated surfaces with activation energies of approximately 2.00 ± 0.02 eV. The reaction pathways indicate that NH<sub>3</sub> adsorbs via similar mechanisms on both surfaces, resulting in comparable nitridation kinetics. Furthermore, this study suggests that highly reactive NH<sub>2</sub><sup>−</sup> species generated in the gas phase from ionized NH<sub>3</sub> may help reduce the process temperature in the GaN-ALD process. |
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| ISSN: | 2076-3417 |