Characterisation of UHV-CVD (ultra high vacuum chemical vapour deposition) grown Si/SiGe heterostructure field-effect transistor (HFET) material with a buried, strained silicon layer has been carried out using non-destructive optical techniques. The effect of thermal budget on the heterostructure was investigated by annealing samples at temperatures up to 900 degrees C for 5 min and carrying out analysis using Raman back-scattering spectroscopy. An investigation of silicon cap loss due to native oxide removal etches was carried out using phase modulated variable angle spectroscopic ellipsometry (VASE) and correlated with Rutherford back-scattering spectroscopy (RBS) measurements.