Sharp-Line Donor-Acceptor Pair Spectra in AlSb

We have observed sharp-line donor-acceptor pair spectra (type I) in Se-doped AlSb. We analyze the spectra quantitatively by using a known solution of the Schrödinger equation for an electron bound to a dipole of finite charge separation. Excellent agreement is obtained between the theoretically predicted and experimentally observed spectra for the parameters $E_g=1.69\mathrm{}$ eV, $E_D=0.15\mathrm{}$ eV, $E_A=0.04\mathrm{}$ eV, and an electron Bohr radius $a_e=4.28\mathrm{}$ Å.