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

Abstract

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 P3/2 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 [1] using grating spectrometers.