Unfortunately, HL2 uses a different method with the materials system.
vTEX/XWAD will create files in the forms of vtf and vmt. the vtf is the texture itself, in a modified targa format. the vmt file is a simple text file that defines all attribues of the texture - what lighting method it will use (VertexLitGeneric or Lightmapped Generic, for models and world respectively) and any additional info, like what sort of shader it should have, or to render a certain portion of the texture invisible for alpha-textures.