Abstract
The Er-doped InGaAsP epitaxial layers with a wavelength of 1.1 μm lattice-matched to InP have been grown by liquid-phase epitaxy. When the Er amount doped in the InGaAsP growth solution is lower than 0.21 wt%, it usually has a fairly shiny, smooth surface morphology and a flat interface between epitaxial layer and substrate. By the wavelength-dispersive-X-ray-spectrometry analysis, we find the Ga solid composition maintains the same as that in the undoped layer, while the As solid composition decreases linearly with increasing Er wt%. The lattice mismatch between InGaAsP layer and InP substrate also decreases linearly with the Er wt% in the growth solution. It may be due to the formation of microparticles of Er-rich compounds ErAs. All the Er-doped samples still exhibit n-type conduction, but its electron concentration decreases with increasing Er wt% and is one to two orders of magnitude lower than those of undoped layers. By the photoluminescence (PL) measurements at various temperatures and excitation levels from the undoped InGaAsP layers, we identify the three peaks associated with the near-band-to-band, shallow- and deep-donor-to-acceptor-pair transitions. However, the deep- and shallow-donor-to-acceptor recombination peaks will sequentially disappear with increasing Er wt% for the Er-doped layers. As the Er amount is above 0.54 wt%, only the near-band-to-band peak dominates the PL spectra and exhibit a full width at half maximum of 9.3 meV. These results can be attributed to the donor gettering in the presence of Er. In addition, the PL peak wavelength decreases linearly with increasing Er wt% due to the variations of solid composition and lattice mismatch in the Er-doped quaternary layers.