Photoluminescence excitation spectra from undoped InP

In extremely pure InP when samples are annealed, five sharp emissions labeled by X_i (i = 1-4) and W were observed slightly below bound exciton emissions. Selectively-excited photoluminescence and photoluminescence excitation measurements were made to examine the features of these five emissions in the spectrum of annealed undoped InP. Four sharp emissions were observed below bound exciton emissions in undoped InP when samples were annealed at above 350°C. Through low temperature photoluminescence excitation (PLE) spectroscopy, it was confirmed that these emissions are closely related with donor impurities. An additional sharp emission observed below the well-established donor-acceptor emission, denoted by W was also determined for the first time to be associated with the acceptor. It was concluded that PLE spectroscopy is a very powerful method to identify the origins of radiative transitions