Noncontacting laser photocarrier radiometric depth profilometry of harmonically modulated band bending in the space-charge layer at doped SiO2-Si interfaces

Abstract

Laser infrared photocarrier radiometry (PCR) was used with a harmonically modulated low-power laser pump and a superposed dc superband-gap optical bias (a secondary laser beam) to control and monitor the space-charge-layer (SCL) width in oxidized $p\text{‐}\mathrm{Si}\text{–}\mathrm{Si}{\mathrm{O}}_2$ and $n\text{‐}\mathrm{Si}\text{–}\mathrm{Si}{\mathrm{O}}_2$ interfaces (wafers) exhibiting charged interface-state related band bending. Applying the theory of PCR-SCL dynamics [A. Mandelis, J. Appl. Phys. 97, 083508 (2005)] to the experiments yielded various transport parameters of the samples as well as depth profiles of the SCL exhibiting complete ( $p$ -type Si) or partial ($n$ -type Si) band flattening, to a degree controlled by widely different minority-carrier capture cross section at each interface. The uncompensated charge density at the interface was also calculated from the theory.