Preparation And Properties Of GaN/TiO_2-x Heterojunction

In recent decades,with the rapid advancement of industrialization and the continuous growth of the global economy and population,environmental pollution,climate change and energy shortage have become great challenges.Under this background,technologies such as solar power generation and photocatalytic degradation have emerged.The research on semiconductor materials with a wide range of light absorption,high carrier separation and high photoelectric conversion efficiency has become a research hotspot.Gallium nitride and titanium dioxide have the advantages of great chemical stability and low photo-corrosion.In this paper,Ga₂O₃/TiO₂ powders were prepared by sol-gel method and nitrided to obtain GaN/TiO_2-x powders.The influences of nitriding temperature and stoichiometric ratio of Ga and Ti on the phase,microstructure and photoelectric properties of the samples were investigated.（1）Ga₂O₃/TiO₂ powder was prepared using gallium nitrate and titanium dioxide nanopowder.The sample was nitrided at different temperatures to obtain a GaN/TiO_2-x powder.Field emission scanning electron microscopy（FESEM）,X-raydiffractometry（XRD）,UV-Visspectrophotometer（UV）,fluorospectrophotometer（PL）,surface photovoltage spectrometer（SPV）,electrochemical workstation were used to study the effects of nitriding temperature on the phase composition,morphology and photoelectric properties of the samples.The results show that the higher the nitriding temperature,the higher the degree of nitriding of Ga₂O₃,and the better the crystallinity of GaN.When nitriding at 700°C,TiO₂ remains in its original state,no phase change and reduction reaction occurs;when the nitriding temperature reaches 750°C,TiO₂ in the sample begins to be gradually reduced to TiO_2-x,and with the increase of temperature,the greater the degree of reduction,the greater the amount of TiO_2-x.Almost no TiO₂ was observed in the sample from 800°C.The UV-visible absorption data showed that the absorption range of sample nitrided in 700°C was the largest,the band gap of sample nitrided in 900°C was the narrowest,and the absorbance increased with the increase of the nitridation temperature.Electrochemical test results show that the sample nitrided at 800°C has moderate conductivity,high carrier concentration,and the highest separation efficiency.At-0.8 V（vs.Ag/AgCl）bias,The photocurrent density of the sample nitrided at800°C.is the highest.（2）Ga₂O₃/TiO₂ powders with different stoichiometric ratios of Ga and Ti were prepared by sol-gel method,and the samples were nitrided at an optimum temperature of 800°C to obtain GaN/TiO_2-x powder samples.The characterization and test results show that when the ratio of Ga and Ti is 1:2,after nitriding at800°C for 1 h,there are a large number of unreduced TiO₂ in addition to GaN and TiO_2-x.When the ratio is 1:1 and 2:1,TiO₂ is reduced to TiO_2-x,and as the Ti content decreases,the intensity of TiO_2-x peak weakens and the GaN peak intensity increases.From the viewpoint of absorbance,the sample 1:2>1:1>2:1indicates that the increase of the black TiO_2-x ratio can improve the absorption capacity of the sample.From the value of the forbidden band width,the larger the TiO_2-x ratio,the narrower the band gap of the sample.Electrochemical test results show that the sample with an 1:1 stoichiometric ratio of Ga and Ti has the best conductivity,the highest carrier concentration,and the maximum value of photocurrent density,reaching 30.72μA/cm².