Green chip makers face a choice: ALD costs the planet more than CVD

Gallium nitride (GaN) is a wide-bandgap semiconductor that forms a cornerstone in several electronic devices in modern society, such as light-emitting diodes and chargers for computers and phones. Gallium production is increasing rapidly in response to rising demand, with direct implications for raw material extraction and energy consumption. Yet the environmental footprint of producing devices of GaN remains largely unexplored. A key step in making a GaN-based device is to deposit a thin film of GaN on a substrate. We present a cradle-to-gate life cycle assessment (LCA) of GaN deposition via atomic layer deposition (ALD) and chemical vapor deposition (CVD), incorporating process-level inputs and outputs. The analysis compares scenarios that include or exclude the silicon substrate and use alternative geographic electricity mixes. Our study shows that the electricity consumption and use of metal organic precursors for Ga are the environmental hotspots in both ALD and CVD of GaN. This makes the sustainability of production highly dependent on electricity generation. Depositions using ALD exhibit higher sustainability burdens than CVD across most impact categories, despite the much lower process temperature in ALD. This is driven by upstream precursor production and process energy demands. By including the silicon wafer in the LCA, impact dominance shifted to upstream substrate manufacturing. These results clarify the key environmental hotspots in GaN deposition and provide a basis for targeted mitigation strategies in semiconductor process design.