Controlled ALD Doping of Er3+ for Active On-Chip Waveguide Amplifiers Based on Al2O3

In this work, we report on the development of ALD-grown ultralow loss host Al2O3 planar waveguides on Si and then successful realization of ALD-grown Er3+ doped on-chip Al2O3 waveguide-based high-gain amplifier devices. Both thermal and plasma enhanced ALD processes have been employed in the optimization processes. Optimization of both Al2O3 and Er2O3 growth conditions is performed for fine-tuning the optical properties of respective films. Systematic characterization of both films has been carried out by making use of spectroscopic ellipsometry, XRD, FTIR, and XPS techniques. The Er2O3 layers are sandwiched between the Al2O3 layers to achieve controlled erbium ion doping with the homogenous distribution. The effects of the growth parameters of Al2O3 and Er2O3 including deposition temperature, RF plasma power, TMA pulse time, Er(thd) 3 pulse time, and O-2 pulse time are optimized With this work, we propose a method for precise control of doping ion concentration and its distribution. As a demonstrator, single-mode ridge waveguide amplifiers are realized by lithography from the active planar structures. ALD deposited chip-scale single-mode Er3+ doped Al2O3 ridge waveguide amplifiers with a small-signal gain of more than 13 dB/cm over the C band are realized. The reported ALD based growth process can further be adapted for active ion doping of different oxide systems with precise concentration and profile control, thus offering new opportunities for active on-chip applications.