Low-temperature Growth And Characteristics Of GaN/g-C₃N₄ Heterojunction

An outstanding alloy system（InxGa1-xN and AlxGa1-xN）with its continuous adjustment of band gap width from 0.7eV（InN）to 6.2eV（AlN）can be obtained in group III-Ⅴnitrides（GaN,AlN,InN）belonging to a composite wurtzite structure by appropriately adjusting alloy composition,resulting in the realization of the coverage of red,yellow,blue,green,purple and ultraviolet spectrum in manufacturing photoelectric component.In addition,GaN semiconductor materials with great electrical characteristics such as higher electron mobility,higher electron drift saturation velocity and higher critical breakdown electric field,as well as low dielectric constant etc.have remarkable potential in applications of high-temperature,high-frequency and high-power photoelectric devices.Graphite-like carbon nitride（g-C₃N₄）is widely used in semiconductor materials due to its excellent properties including excellent electrical conductivity and good adsorption properties,high quantum yield as well as good optical activity etc.Moreover,the surface structure of g-C₃N₄ and GaN are both hexagonal,with the calculated lattice mismatch of 14.8%,which is lower than the lattice mismatch between GaN and the currently commonly used sapphire substrateα-Al₂O₃（16.7%）.Therefore,the epitaxial growth of GaN thin films on g-C₃N₄ with good electrical conductivity can not only reduce the mismatch dislocation density and stress the warpage of crystal grains,but also facilitate the enhancement of vertical GaN devices by means of the combination of semiconductor heterojunctions.In this paper GaN/g-C₃N₄ heterojunctions were synthesized by a low-temperature growth and their characteristics were investigated.The plasma enhanced metal organic chemical vapor deposition（ECR-PEMOCVD）was used for the low-temperature growth of GaN/g-C₃N₄ heterojunctions,with transparent conductive glass（ITO）as the substrate,and g-C₃N₄ deposited at low temperature as the intermediate layer,and trimethyl gallium（TMGa）as the gallium source,and H₂ As a carrier gas,as well as a purity of99.999%nitrogen as a nitrogen source.The results as follows:light yellow transparent g-C₃N₄ films with the smooth and uniform appearance are successfully deposited on the ITO substrate at a temperature of 550℃by CVD in a tube furnace,with 0.65g of melamine C₃N₃（NH₂）₃ powder as a precursor material.Then,the GaN films are grown on g-C₃N₄/ITO substrates by ECR-PEMOCVD equipment.XRD results showed that the c-axis preferentially grown GaN film on g-C₃N₄/ITO can be carried out with appropriate growth parameters.The results showed that the 430℃-grown GaN films with the c-axis（002）preferred orientation with the compressive stress value of 0.35GPa,the grain size of42.1nm,and the luminescence peak position of 3.48eV as well as the small surface roughness of 19.7nm indicate good crystalline quality.The analysis of electrical properties showed that the ITO substrate and the heterojunction GaN/g-C₃N₄ is close to Schottky contact and the surface defects of GaN are relatively small.These results will lay an important research foundation for the preparation of multifunctional and miniaturized sensors.