Homogeneity assessment of large‐diameter III‐V compound semiconductor substrates by near‐infrared transmittance measurement

Abstract

The light absorption mechanisms below the fundamental energy gap in undoped and Si-doped GaAs crystals have been investigated to assess EL2 defects and the carrier concentration distribution in III-V compound semiconductor substrates. It is demonstrated, that the near-infrared transmittance mapping equipment consisting of a high-brigthness LED, a high-sensitivity CCD camera, and a digital image processing system is capable to reveal surface scratches and local crystal imperfections such as inclusions, voids, and twining inside the substrate, besides EL2 defects and the carrier concentration distribution. Hence, the homogeneity of III-V compound semiconductor substrates with diameter up to 6 inches can be assessed in less than several seconds with high spatial resolution of 640×480 pixels.