【Member Papers】Energy-band engineering and deep-ultraviolet photodetection of Ga₂O₃ alloys: a concise review

      Researchers from the Inner Mongolia University and Nanjing University of Posts and Telecommunications have published a dissertation titled "Energy-band engineering and deep-ultraviolet photodetection of Ga₂O₃ alloys: a concise review" in Nanotechnology.

Project Support

      This work is supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 62204125), the Inner Mongolia University Experimental Technology Research Project in 2025 (Self-Made and Modified Equipment Project) (Grant No. SYJS2025004), the Steed Plan of Inner Mongolia University for Introducing High-Level Talents (Grant Nos. 10000-23112101/285 and 10000-23112101/277), the Program for Innovative Research Team in Universities of Inner Mongolia Autonomous Region (GrantNo.NMGIRT2503), the Joint Funds of the Natural Science Foundation of China (Grant No. U23A20349), the Key Technology Project of Suzhou City (Grant No. SYG2024003),and the Jiangsu Provincial Team of Innovation and Entrepreneurship(GrantNo.JSSCTD202351).

Abstract

      Gallium oxide (Ga₂O₃)-based solar-blind ultraviolet photodetectors gained much attention for their promising prospects in new-generation solid-state optoelectronics and electronics. Catering for the demands of broadband photodetection, tunable energy-band, adjusted carrier concentration and effective carrier transition, alloying engineering through doping is gradually launched as one of the research emphases. This review is proposed to understand the photodetection performances in view of energy-band engineering. Especially for the representative (In_xGa₁₋x)₂O₃ and (Al_yGa₁₋y)₂O₃ alloys, the conduction band edges upshift as the empty Al 3 s and In 5 s states are introduced with higher energy, hybridize with Ga 4 s state. This leads to a result that low effective electron mass and high electron mobility could be achieved, contributing to high quality tunable performances of solar-blind UV photodetection. Thus, in this concise review article, the alloyed Ga₂O₃ for photodetection would be reviewed and discussed based on the current developments, from the viewpoint of energy-band theory.

Outlook and perspectives

      In summary, this concise review has highlighted significant progress and ongoing efforts in energy-band engineering and tunable deep UV (DUV) photodetection. Alloying—particularly with similarly structured group III elements like In and Al—as well as doping with other elements (e.g., N, Ir, Ti, Zn) or managing intrinsic defects, provides powerful routes to modulate the bandgap, adjust carrier concentration, and modify carrier transport dynamics. These capabilities are crucial for optimizing photodetector performance, including wavelength selectivity, photoresponsivity, and response speed, catering to diverse applications from flame sensing to secure communication.

      Despite the promising advancements, several key challenges and exciting opportunities remain:

      1.P-type doping: Achieving stable, reliable, and efficient p-type conductivity in wide-bandgap Ga₂O₃ and its alloys remains a critical bottleneck. While some progress has been made (e.g., N-doping, Ir-alloying), overcoming issues such as self-compensation by native defects and low acceptor solubility is paramount for realizing high-performance bipolar devices like p–n homojunctions. Future work exploring novel acceptor dopants, co-doping strategies, or non-equilibrium growth techniques is essential.

      2.Defect control and understanding: While doping and alloying enable bandgap tuning, they inevitably introduce defects (point defects, complexes, dislocations, grain boundaries). These defects can act as trapping or recombination centers, detrimentally affecting carrier lifetime, mobility, and device stability. A deeper understanding of defect formation mechanisms, their energy levels within the bandgap, and their precise impact on optoelectronic properties—assisted by advanced characterization and synergistic computational modeling—is crucial. Developing effective defect passivation or mitigation strategies during material growth and device processing is a key area for improvement.

      3.Alloy homogeneity and phase stability: Achieving uniform composition and maintaining phase stability, especially at higher alloying concentrations needed for significant bandgap shifts, can be challenging due to lattice mismatch and differing thermodynamic properties. Further optimization of growth techniques is needed to minimize phase segregation and structural imperfections that degrade material quality and device performance.

      4.Device integration and reliability: Translating improved material properties into robust, reliable, and manufacturable devices requires overcoming challenges in contact formation, surface passivation, device packaging, and long-term stability under operational stress.

      Looking forward, the field of Ga₂O₃ alloy-based DUV photodetectors holds immense potential. Continued interdisciplinary efforts combining materials science, physics, chemistry, and device engineering will be vital. Addressing the aforementioned challenges will pave the way for next-generation DUV optoelectronic devices with unprecedented performance and functionalities, impacting fields ranging from environmental monitoring and industrial process control to defense and space exploration.