A deposition system which is configured to enable improved temperature uniformity of a heated substrate may include a susceptor provided in a chamber to hold a substrate, a reflection housing provided outside the chamber, a heating module including light sources provided in the reflection housing, and a reflection control module provided in the reflection housing between the heat sources and the chamber. The reflection control module may be configured to reflect light, which propagates along a first trajectory from the light sources toward a center region of the substrate, to propagate along a second trajectory toward an edge region of the substrate, thereby providing improved substrate irradiance uniformity and thus improved substrate temperature uniformity. Improved substrate temperature uniformity may result in improved thickness uniformity of layers provided on the substrate in a deposition process.