Radiative Recombination between Deep-Donor-Acceptor Pairs in GaP

Abstract

A number of emission bands lying several tenths of an eV below the band gap have been observed in photoluminescence spectra of GaP crystals. These bands shift in peak position as different donors and acceptors are incorporated in the crystals. The emission bands are identified as donor-acceptor pair recombination bands involving deep levels by noting that these shifts correspond directly to changes in the donor and acceptor binding energies and by noting their similarity to shallow donor-acceptor pair bands previously identified as such. One of these bands is due to recombination between the deep donor oxygen and the shallow acceptor zinc. In p-type crystals thermal ionization of minority carriers trapped on the deep donor is small, so that in samples containing optimum concentrations of zinc and oxygen, photoluminescence (external) quantum efficiencies as high as 1.5% have been measured at room temperature.