NONCONTACT AND NONDESTRUCTIVE MEASUREMENT OF CARRIER CONCENTRATION OFNITROGEN-DOPED ZNSE BY REFLECTANCE DIFFERENCE SPECTROSCOPY

We report an optical technique to determine the net carrier concentrat ion 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 n ear 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 a lso address the origin of the surface roughness induced baseline in th e RD spectra which affects the accuracy of the measurement.