AN APPROACH TO THE ENERGY-GAP DETERMINATION FROM REFLECTANCE MEASUREMENTS

A method to obtain the band gap energy value from reflectance measurem ents has been developed for bulk materials with direct and indirect ga ps. In an energy region around the gap value, the experimental reflect ivity is fitted by two functions of the type R=A(0)+A(1)'(1/h nu)(2)-A (1)'E-g x (1/h nu)(3) and R=A(0)+B[(h nu-E-g)/(h nu)](4), for direct a nd indirect transitions, respectively, in an energy range around the g ap value. This implies that the absorption coefficient, alpha, shows a dependence with the energy alpha=(A/h nu)(h nu-E-g)(m) with m=1/2, 2 for direct and indirect gaps, respectively. The method has been checke d in several materials of known energy gaps including Si and Ge. (C) 1 998 American Institute of Physics.