Infrared spectra of new acceptor levels in indium- or aluminum-doped silicon

Infrared absorption measurements have verified the existence of shallower acceptor levels associated with both indium and aluminum in silicon. The new spectra correspond to effective-mass-like acceptors with optical ionization energies of 112.8±0.3 meV in indium-doped silicon and 56.3±0.3 meV in aluminum-doped silicon. The existence of the shallower acceptor level in aluminum-doped silicon has been further verified by Hall coefficient measurements.