Infrared Absorption Spectra of Compensated Single Crystal Silicon using a Fourier Transform Spectrometer

摘要

Summary form only given. The infrared absorption spectra of crystalline silicon containing some impurities have been studied in the 200 to 2000 cm^{-1 region using Fourier transform infrared (FTIR) techniques. The excitation spectra associated with the group III acceptor impurities boron and indium and the group V donors, antimony and phosphorus, have been studied at helium temperatures. Fig. 1 shows the schematic and highly simplified energy momentum diagram, and the various electronic transitions due to shallow donors and acceptor (hole transition) centers. Fig. 2 shows the room and 15K spectra of compensated silicon some 0.12 inches thick. The most significant change in the low temperature spectrum is the decrease in absorption and the addition of intense bands in the far infrared region. Fig. 3 shows an expanded plot of two samples at 15K in the 450-150 cm-1 region, in which the P_3/2 set of transitions for boron are observed. A line seen at 316.1 cm-1 is that of phosphorus, which may be compared to previous measurements using grating spectrometers. Of further interest is the observation of two or more acceptor impurities in silicon. Fig. 4 records the 20K and 300K spectra. The spectra reported here were obtained in about one minute measurement time. The low temperature spectrum of In:Si demonstrates it is possible to rapidly detect small amounts of boron dopants in the silicon lattice. From Hall measurements, the crystal had NA-ND-1013 atoms cm-3 and indicates that boron concentrations of order 1012 atoms cm-3 can be detected. Extra fine features found in the spectra of current intense interest for these important detector crystals are also discussed.}