Absorption coefficient, energy gap, exciton binding energy, and recombination lifetime of GaN obtained from transmission measurements

The absorption coefficient for a 0.4-mu m-thick GaN layer grown on a polished sapphire substrate was determined from transmission measurements at room temperature. A strong, well defined exciton peak for the A and B excitons was obtained. The A, B, and C excitonic features are clearly defined at 77 K. At room temperature, an energy gap E-g=3.452+/-0.001 eV and an exciton binding energy E-x(A,B)=20.4+/-0.5 meV for the A and B excitons and E-x(C)=23.5+/-0.5 meV for the C exciton were determined by analysis of the absorption coefficient. From this measured absorption coefficient, together with the detailed balance approach of van Roosbroek and Shockley, the radiative constant B=1.1X10(-8) cm(3)/s was obtained. (C) 1997 American Institute of Physics. [S0003-6951(97)01344-2].