Novel electronic design for double-modulation spectroscopy of semiconductor and semiconductor microstructures

The double-modulation reflectance technique has proven to be a powerful characterization tool of semiconductors applied in high-background–light-interference systems. In this article, we present a novel and inexpensive electronic-circuit design for implementing the double-modulation measurements using only one lock-in amplifier. The electronic design is fabricated in an accessory hardware of modulation spectroscopy which can easily select the double- or single-modulation mode via a manual switch. Detailed design diagrams of the electronic hardware are described. Measurements of some representative samples of semiconductors and actual device structures are carried out. Experimental results demonstrated the well-behaved performance of this design.