Piezoelectric Photothermal and Surface Photo-Voltage Studies of Carrier Recombination Mechanism at Interface of Si p–n Junction

Abstract

Room-temperature piezoelectric photothermal spectroscopy (PPTS) and surface photo-voltage spectroscopy (SPVS) were carried out on two types of Si p–n junction sample to investigate carrier recombination processes at the interface. It was found that the SPVS peak positions of each spectrum depend on the direction of illumination: a 1.18 eV peak for substrate-side illumination and a 1.25 eV peak for epitaxial-layer-side illumination. We concluded that peak position corresponds to the specific photon energy at which optical penetration length is equal to the distance from the irradiated surface to the p–n junction. On the contrary, the PPTS peak positions depended on the structure of the samples: a 1.18 eV peak for the p/N sample and a 1.25 eV peak for the n/P sample. The PPTS amplitude spectrum of the n/P sample split into two distinctive peaks as a result of frequency being increased. One was a 1.25 eV peak, whose origin is not clear yet. The other was a newly appearing 1.18 eV peak, whose position corresponds to that shown by SPVS.