Washington, Aug. 6 (CNA) U.S. President Donald Trump signed an executive order Thursday imposing minimum import prices (MIP) and a 15 percent tariff on polysilicon -- the primary raw material used to manufacture semiconductors and solar panels -- and related products. However, for imports from Japan, South Korea, Taiwan, Switzerland, Liechtenstein and European Union member states, the combined tariff rate will be capped at 15 percent. Screenshot from the White House's websiteThe minimum import prices are set at US$21 per kilogram for polysilicon, US$100 per kilogram for polysilicon ingots and wafers, US$0.22 per watt for solar cells and US$0.38 per watt for solar modules. The measures follow a year-long investigation by the U.S. Department of Commerce, which found that imports had "eroded" the capacity of the U.S. polysilicon industry. "These tariffs -- combined with the MIP program -- will promote United States production of polysilicon derivatives by ensuring a commercially viable market for them," Trump said in the statement.