A substrate carrier door assembly including relatively high sealing force that can be modulated. Substrate carrier door assembly includes a carrier door configured to seal to a carrier body, a first attraction member on the carrier body, and a second attraction member on the carrier door. Attraction members are selected from a group of a magnetic material and a permanent magnet. Substrate carrier door assembly includes a magnetic field generator energizable to reduce attraction force between the attraction members making the carrier door relatively easier to remove, yet providing enhanced sealing when not energized. Substrate carriers including the substrate carrier door assembly and methods of processing substrates are provided. A substrate carrier including a port configured to allow gas to be injected into, or removed from, a carrier chamber, and a magnetic port seal is also disclosed, as are numerous other aspects.