Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV

Abstract

The absorption coefficient α for GaAs at room temperature was determined in the spectral range from 1.3 to 1.6 eV by transmission measurements for 10⩽α⩽10³ cm⁻¹ and by a Kramers−Kronig analysis of the reflectance for α≳10³ cm⁻¹. Measurements were made on high−purity n−type samples, n−type samples with free−electron concentrations from 5×10¹⁶ to 6.7×10¹⁸ cm⁻³, p−type samples with free−hole concentrations from 1.5×10¹⁶ to 1.6×10¹⁹ cm⁻³, and p−type samples heavily doped with the amphoteric impurity Si. These data show that near the direct energy gap E_g the shape of the α−vs−photon−energy curve is strongly dependent on the impurity concentration.