Atomic-Layer-Ti-Doped Ga2O3 Thin Films with Tunable Optical Properties and Wide Ultraviolet Optoelectronic Responses

Doping and alloying in Ga2O3 to tune electronic and photonic behaviors is still urgent but challenging, whereas Ga2O3 has shown great promise in deep-ultraviolet (DUV) photodetectors and functional high-power devices. Herein, atomic-layer-Ti-doped/incorporating Ga2O3 (TGO) thin films with tailored optical properties in the UV region from 200 to 400 nm are described. The Ti content in amorphous TGO thin films is controlled and adjusted up to 11 at% during a plasma-enhanced atomic layer deposition (PE-ALD) process. The composition-dependent optical constants of both amorphous and polycrystalline TGO thin films are analyzed in the wavelength region of 200-800 nm through spectroscopic ellipsometry (SE) with a point-by-point fitting method. An obvious bandgap tuning effect and redshifted absorption edges are observed in the transmittance spectra of TGO thin films with increasing Ti concentration. Moreover, composition-dependent optical constants and wide absorption are also verified by the significant and broadened DUV photoelectronic responses of TGO-based photodetectors. It is believed that this work will help in understanding the DUV optical constants and bandgap transitions of TGO thin films used for functional optical devices in the UV region below 400 nm.