ATOMIC CONFIGURATION OF THE ER-O LUMINESCENCE CENTER IN ER-DOPED GAAS WITH OXYGEN CODOPING

This article investigates the structure of an Er luminescence center in GaAs by using its intra-4f-shell luminescence spectrum as an atomic probe to identify the atomic configuration. This Er center is formed in GaAs by metalorganic chemical vapor deposition with O codoping and the center shows a high efficiency and a sharp luminescence spectrum under above-band-gap photoexcitation. A single luminescence line in the spectrum of a GaAs:Er,O splits into more than eight lines in the spectrum of Al0.01Ga0.99As:Er,O. This drastic change due to the addition of 1% Al can be explained by assuming that, because of the high tendency of Al atoms to react with O atoms, the Al atoms preferentially occupy the nearest-neighbor Ga sites of two O atoms, both of which are coupled with the Er atom. Based on the luminescence spectra and additional experiments of Rutherford backscattering and secondary ion mass spectroscopy, we propose that the structure of the Er luminescence center under study is Er occupying the Ga sublattice with two O atoms most likely located at the nearest-neighbor As sites. An Er-related spectrum of GaAs0.97P0.03:Er,O can also be understood based on this model if the chemical difference of Al and P is taken into account.