Quick mapping of carrier concentration in InP substrate with large diameter by near-infrared transmittance measurement

In order to assess macroscopic and microscopic profiles of carrier concentration in n-type InP substrates, near-infrared (NIR) transmittance has been measured and quantitatively converted into the term of carrier concentration with the calibration curve determined experimentally in the range from 1×1018 to 6.4×1018 cm−3. The InP substrate assessed here was a 4-in S-doped substrate grown by the vapor-pressure-controlled Czochralski (VCZ) technique. It was found that the radial profile of carrier concentration was macroscopically concave. An elliptical striation pattern due to microscopic fluctuation of carrier concentration was observed, which seemed to be originating from unwanted asymmetry in the VCZ growth process. The macroscopic and microscopic profiles of carrier concentration may provide very important information about the crystal growth situations such as the shape of solid–liquid interface and the stability of crystal growth.