Method and apparatus for analysis of material composition

A method is provided of analysing the composition of a semiconductor material ( 3 ) comprising irradiating the material with energy from an energy source ( 1 ) which energy is diffracted from the material, detecting one or more portions of the diffracted energy, and analysing the or each detected portion to obtain a parameter indicative of the intensity of the or each portion. The or each portion of the diffracted energy detected may be a quasi-forbidden reflection diffracted from the material, e.g. may be a ( 002 ) reflection diffracted from the material, or a ( 006 ) reflection. The detection of the or each portion of the diffracted energy may take place at one or more detection angles ( 9 ), or at all angles of reflection/transmission of the diffracted energy source, or at a range of angles around one or more detection angles. The energy source may comprise a beam of x-rays produced by an x-ray tube ( 2 ), and one or more detectors ( 4 ) may be used to detect the or each portion of the diffracted energy.