Nondestructive Measurement of Carrier Density in GaAs Using Relative Reflectivity of Two Terahertz Waves

Abstract

A new nondestructive method using terahertz waves for determining the carrier density of GaAs is proposed. The reflectance around the longitudinal optical (LO) phonon frequency changes with carrier density, whereas the reflectance around the transverse optical (TO) phonon frequency is constant. The relative reflectance, which is evaluated from the reflectance at the two frequencies related to the TO and LO phonon, as a function of the carrier density of GaAs was calculated from the dielectric function. A broadband tunable terahertz source is convenient for producing two waves around these phonon frequencies. Imaging of n-type GaAs wafer using this new terahertz method is described.