Intrinsic, Doped And Alloyed Gallium Oxide Films For Optoelectronics

Due to the impressive advancement of present technology and increasing energy consumption, there is increasing demand for energy-efficient multifunctional devices based on low-cost, eco-friendly material systems. Gallium oxide (Ga2O3) is an emerging semiconductor with potential for the next generation of power electronics and optoelectronic devices due to its ultra-wide bandgap of 4.8 eV and high theoretical breakdown voltage of 8 MV/cm among other intrinsic properties. Some of the possible applications of β-Ga2O3 include ultra-violet (UV) solar blind photodetectors, field effect transistors, solar cells, and chemical sensors. However, to utilize its full potential, understanding the mechanistic aspects of thin film growth and optimization of the phase and properties is desirable. In recent years, significant attention directed towards the structure, characteristics, and performance of Ga2O3 thin films by a wide variety of physical and chemical methods in addition to using a variety of dopants, alloying elements, and processing techniques. In the present work, we adopted pulsed-laser deposition (PLD), which is quite successful in preparing high quality oxides. PLD has been explored for the epitaxial growth of superconducting oxides, but the efforts are relatively scarce towards Ga2O3 and its polymorphs. On the other hand, among other physical deposition methods, PLD facilitates high-quality multi-component films because of the extensive target selection and controllable processing conditions. Therefore, in this project, we directed our efforts to deposit both intrinsic and alloyed Ga2O3 films using PLD. We systematically investigated the effect of processing conditions and variable dopants (or alloying elements) to establish the road map to optimize the unique and otherwise not possible phases of Ga2O3. In our research, specific attention was directed towards the Ga2O3 alloyed with W and Sn in order to design efficient materials for advanced photodetectors. The PLD samples were characterized using a wide variety of analytical techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), atom-probe tomography (APT), X-ray photoelectron spectroscopy (XPS). These studies allowed us to understand the structure, phase, microstructures, and surface chemistry of the samples and the effect of W and Sn as dopants into Ga2O3. The effect of processing conditions on the optical properties of the W- Ga2O3 and Sn-Ga2O3 PLD films studied by ultraviolet-visible (UV-Vis) spectroscopy and photoluminescence (PL) measurements. Lastly, the fabricated films were integrated deep UV-photodetectors, which were characterized to demonstrate their functional device performance. The processing conditions were optimized to produce high quality PLD Ga2O3 films with demonstrated performance in deep UV-photodetectors.