Fine structure due to donor-acceptor pair luminescence in compensated Si

A fine structure on the higher energy side of donor-acceptor (DA) pair luminescence at 4.2K has been analyzed in compensated Si involving P donors and B acceptors. We calculated the density distribution of DA pairs against photon energy from the number of pairs as a function of the transition energy of respective pairs. A close agreement was obtained between the density curve and the observed spectral structure using the generally accepted values of energy gap and P donor and B acceptor ionization energies. This allows us to conclude that the structure is due to discrete DA pair recombination.