Thin Film Growth by Low-Pressure Chemical Vapor Deposition System:
Using a custom-designed LPCVD system, single-crystal β-Ga₂O₃ and r-GeO₂ thin films were successfully grown heteroepitaxially on substrates such as sapphire, SiC, and r-TiO₂. The overall structure of the growth system is shown in Figure 1. By obtaining sub-oxide vapors from elemental and compound solid sources, their transfer was achieved with argon, and growth on the substrate was realized in the presence of oxygen gas under suitable system pressure and growth temperature conditions.
Figure 1. Schematic design of the custom-built low-pressure chemical vapor deposition (LPCVD) system for oxide compounds
Power Electronics:
Power electronics is a field of engineering that studies the conversion, control, and efficient transmission of electrical energy. Its main objective is to convert electrical energy from one form to another with minimal losses. These conversions include processes such as AC to DC (rectification), DC to AC (inversion), DC to DC (switched-mode regulators), and AC to AC (frequency converters).
Major Sectors:
Among the most common power electronic devices are diodes, thyristors, MOSFETs, and IGBTs. Diodes allow unidirectional current flow and are mainly used in rectifier circuits. Thyristors enable the control of AC current in high-power applications. MOSFETs are preferred in low- and medium-power applications due to their high switching speeds, while IGBTs are widely used in industrial systems that require high voltage and current.
The main objective of our projects in this field is to achieve these devices with high efficiency on β-Ga₂O₃- and r-GeO₂-based thin-film semiconductors.
Figure 2. Example geometry of a Schottky power diode.
Solar-Blind Photodetectors:
Solar-blind photodetectors are optoelectronic devices that are sensitive to light specifically in the ultraviolet (UV) region, but unresponsive to visible and infrared wavelengths. This property makes them “blind” to sunlight and enables a high signal-to-noise ratio. Since conventional photodetectors are sensitive to a broad spectrum, they struggle to accurately detect UV signals under the dominant influence of visible and infrared light. This often leads to false signals, particularly in outdoor applications with intense sunlight.
Solar-blind photodetectors eliminate this problem by selectively detecting only UV light. In this way, reliability is enhanced in flame detection, early fire warning systems, biomedical imaging, environmental monitoring, and military applications. They also play a critical role in space research for measuring UV radiation in the upper layers of the atmosphere.
In general, they are designed in photoconductive, metal–semiconductor–metal (MSM), Schottky diode, and p–n junction structures. The devices operate by generating an electric current under light excitation, which is achieved through the absorption of UVC light that creates electron–hole pairs, subsequently drifted and collected at opposite electrodes.
Figure 3. Example design of a vertical Schottky diode photodetector.
Our Projects:
In general, our completed and ongoing projects focus on the growth of single-crystal structures, n-/p-type doping, and the fabrication of basic power electronic and photodetector devices. In addition, we have projects currently in the proposal stage aimed at developing power electronic devices and solar-blind photodetectors.
Completed and Ongoing Projects:
As Principal Investigator:
As Researcher: