Non-contact and non-destructive measurement of carrier concentration of nitrogen-doped ZnSe by reflectance difference spectroscopy

We report an optical technique to determine the net carrier concentration of nitrogen-doped ZnSe, N-a-N-d. An optical anisotropy induced by the built-in held was measured by reflectance difference spectroscopy (RDS). It has been shown that the energy derivative of the RD signal near 5eV is proportional to (N-a - N-d)(1/3) when N-a-N-d > 5 x 10(16) Cm-3. The physical origin of the observed power law is discussed. We also address the origin of the surface roughness induced baseline in the RD spectra which affects the accuracy of the measurement.