【Domestic News】Low Temperature Preparation Technology of Ga₂O₃ Based Solar Blind UV Photodetector, Which is Developed by Ningbo Institute of Materials

  The solar blind ultraviolet photodetector has important applications in the fields of people's livelihood (such as power grid safety monitoring, environmental and biochemical detection, forest fire alarm, medical imaging, etc.), and is the focus of research and development of countries around the world. Gallium oxide has many advantages, such as wide band gap (up to 4.9 eV), high earth crust abundance (China's gallium reserves most in the world), stable physical and chemical properties, etc. It is an ideal active layer material for solar blind detection(cut-off wavelength~280 nm, corresponding photon energy~4.42 eV) . At present, some important progress have been made on gallium oxide solar blind ultraviolet detectors, but the process temperature is generally high. Compared with epitaxial or polycrystalline thin film materials, amorphous semiconductor thin films can be prepared at low temperature and uniformly in a large scale. The research and development of low temperature preparation technology of gallium oxide is imperative. However, it is difficult to densify the amorphous film, and its microstructure and stoichiometry are difficult to effectively control, which makes it difficult to control the carrier concentration and oxygen vacancy inside the Ga₂O₃ active layer. At the same time, it is difficult to synergistically improve the optical responsivity and response time of the device.

  In recent years, the research team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences has been committed to the research on preparation of gallium oxide films as well as their solar blind ultraviolet detectors and the regulation of their physical properties. In the early stage, the team prepared gallium oxide based detectors with high UV visible suppression ratio through solution method, and its power consumption can reach the level of pW.

  Recently, the team effectively controlled the surface roughness, relative mass density, refractive index, band gap and composition ratio (gallium oxygen ratio) of amorphous gallium oxide (a-GaO_x) films by applying an assisted preparation process during which magnetron sputtering and substrate bias voltage are carried out. The a-GaO_x films prepared at near room temperature have fewer defects, which greatly improve the density and carrier mobility of the films. The light response of the corresponding solar blind UV detector is 460 times higher and has good spectral selectivity.

  The team developed a low temperature annealing process induced by metal , which reduced the crystallization temperature of gallium oxide by 200 ℃; They proposed a low temperature induced crystallization mechanism under the combined action of seed layer and non-equilibrium state. After induction, the density of the film is greatly improved, and defect states such as band tail state and oxygen vacancy state are significantly reduced. The corresponding photoelectric thin film transistor detector has excellent spectral selectivity, as shown in Figure 1.

Fig. 1 Low temperature crystallization mechanism and photoelectric performance test of detector

Relevant Achievements

Solution-processed amorphous Ga₂O₃:CdO TFT-type deep-UV photodetectors

DOI: 10.1063/5.0007617

Ceramics International

Substrate-bias-aided preparation and properties of amorphous gallium oxide films and their deep-ultraviolet photodetectors

DOI: 10.1016/j.ceramint.2021.08.105

The Journal of Physical Chemistry Letters

Low-Temperature-Crystallized Ga₂O₃ Thin Films and Their TFT-Type Solar-Blind Photodetectors

DOI: 10.1021/acs.jpclett.2c01852

Project support

International Partnership Program of Chinese Academy of Sciences

Major Program of Zhejiang Natural Science Foundation

Major Breakthroughs in Ningbo