Controlled incorporation of erbium in yttrium oxide thin films for micro-optoelectronic integrated circuits

Incorporation of a high concentration of optically active trivalent erbium (Er3+) with controlled spatial distribution in yttrium oxide (Y2O3) by radical-enhanced atomic layer deposition (ALD) was demonstrated in this study, enabling the fabrication of miniaturized optical amplifiers with sufficient gain for micro-optoelectronic integrated circuits. Adsorption of metal beta-diketonate precursors, Y(TMHD)3 and Er(TMHD)3, followed by surface reactions with O radicals were found to be self-limiting, with O radicals not only effectively removed the beta-diketonate ligands but also created reactive sites for precursor adsorption. Well controlled deposition of stoichiometric Y2O3 and Er2O 3 thin films with minimal carbon incorporation was achieved, yielding a constant deposition rate of ∼0.3 A/cycle from 200-300°C and increasing to 1.5-2.5 A/cycle at 350°C. The atomic force microscopy images revealed fairly smooth films with the root mean square surface roughness less than 5 A for films of 120 A or less, indicating the film growth mode is layer-by-layer. Fairly conformal deposition of Y2O 3 over 0.5-mum features with an aspect ratio of 2 was also demonstrated.;Er-doped Y2O3 thin films were deposited by radical-enhanced ALD of Y2O3 and Er2O3 in an alternating fashion. Well controlled incorporation of a high concentration of Er in Y 2O3 was achieved at low temperatures of 300-350°C. Analysis of the Er LIII X-ray absorption near edge spectra of the 6-14 at.% Er-doped Y2O3 thin films indicated that the Er is in the optically active trivalent state (Er3+). Specifically, the Er3+ ion was found to coordinate with six O, similar to Er3+ in Er2O3, confirmed by extended X-ray absorption fine structure analyses. There was no indication of Er-Er clustering formation, suggesting a complete miscibility of Er3+ in Y2O3 up to at least 14 at.%.;Room-temperature photoluminescence with well-resolved Stark features was observed for 500-900-A thick 6-14 at.% Er-doped Y2O 3 thin films deposited at 350°C. The results are very promising, since the films are fairly thin and no annealing at temperatures above 700°C was needed to optically activate the Er3+ ions. These results validate Y2O3 as the potential host material for Er 3+ and demonstrate that radical-enhanced ALD is a viable technique for synthesizing Er-doped Y2O3 thin films for optical applications.