Yes, there's an XML file. You'll want ShipBlueprintsDefs.XML in \Galactic Civilizations 3\Data\Game\; look for
<!-- Begin Blueprint -->
<ShipBlueprint>
<InternalName>AssaultFighterBlueprint</InternalName>
<ShipHullType>Small</ShipHullType>
<Role>Assault</Role>
<CanBeBuilt>false</CanBeBuilt>
<RequiredComponentType>BeamWeapon</RequiredComponentType>
<RequiredComponentType>MissileWeapon</RequiredComponentType>
<RequiredComponentType>KineticWeapon</RequiredComponentType>
<ComponentType>Armor</ComponentType>
<ComponentType>PointDefense</ComponentType>
<ComponentType>Shields</ComponentType>
<ComponentType>SublightDrive</ComponentType>
<ComponentType>BeamWeapon</ComponentType>
<ComponentType>MissileWeapon</ComponentType>
<ComponentType>KineticWeapon</ComponentType>
<FillerComponentType>BeamWeapon</FillerComponentType>
<FillerComponentType>KineticWeapon</FillerComponentType>
<FillerComponentType>MissileWeapon</FillerComponentType>
</ShipBlueprint>
<!-- Begin Blueprint -->
<ShipBlueprint>
<InternalName>DroneFighterBlueprint</InternalName>
<ShipHullType>Tiny</ShipHullType>
<Role>Interceptor</Role>
<CanBeBuilt>false</CanBeBuilt>
<RequiredComponentType>BeamWeapon</RequiredComponentType>
<RequiredComponentType>SublightDrive</RequiredComponentType>
<ComponentType>BeamWeapon</ComponentType>
<ComponentType>BeamWeapon</ComponentType>
<ComponentType>Shields</ComponentType>
<AllRequiredMustFit>true</AllRequiredMustFit>
</ShipBlueprint>
<!-- Begin Blueprint -->
<ShipBlueprint>
<InternalName>GuardianFighterBlueprint</InternalName>
<ShipHullType>Tiny</ShipHullType>
<Role>Guardian</Role>
<CanBeBuilt>false</CanBeBuilt>
<RequiredComponentType>KineticWeapon</RequiredComponentType>
<RequiredComponentType>Armor</RequiredComponentType>
<ComponentType>KineticWeapon</ComponentType>
<ComponentType>PointDefense</ComponentType>
<ComponentType>Shields</ComponentType>
<AllRequiredMustFit>true</AllRequiredMustFit>
</ShipBlueprint>
There may be one or two others; I'm not really sure. Alternatively, you may be able to create a custom carrier module for your custom fighters, but I'm not certain how you'd do that. I'd start by looking in ShipComponentDefs.XML in \Galactic Civilizations 3\Data\Game\ to see how the base game carriers are handled.