Study On The Epitaxial Growth Of BGaN Film By MOCVD

The forbidden band width of the BGaN alloy material is continuously adjustable from 3.4 to 5.5 eV,and the corresponding emission wavelength is 225 to 365 nm,which can be used for the preparation of ultraviolet light-emitting devices.The BGaN a-axis lattice constants can be perfectly matched with the a-axis lattice constants of AlN and SiC substrates by changing boron component,respectively.These advantages can be used to carry out high-performance GaN-based devices.In addition,there exist isotopes ¹⁰B and ¹¹B in the boron atoms in nature(the atomic ratio ¹⁰B:¹¹B=1:4),and it is possible to take advantage of the larger neutron capture cross section of the ¹⁰B atom to make the neutron detector.However,the epitaxial growth of the BGaN film is greatly affected by the growth parameters,and the boron source?TEB?has a serious problem of pre-reaction with NH₃ during the growth process,which make it difficult to obtain a flat surface morphology and good crystal quality on the one hand.On the other hand,it is difficult to obtain a higher boron component.At present,there is no report on the research of metal-organic compound chemical vapor deposition?MOCVD?epitaxial growth of BGaN films in China.This work is of great significance for promoting the development of domestic BGaN materials and devices and shortening the domestic and abroad gap.In this paper,we used MOCVD technology to perform epitaxial growth of BGaN thin films on sapphire substrates.The specific research work was as follows:1.Research on optimization of BGaN film surface morphology.Using MOCVD technology to epitaxial BGaN films on sapphire substrates,the effects of growth thickness,temperature,pressure and B/III ratio on the surface morphology of BGaN films were studied.The experimental results show that increasing the thickness will deteriorate the surface morphology of the BGaN films;as the temperature increases,the surface morphology of the BGaN films first become better and then deteriorate,the corresponding surface morphology of the BGaN film is best at 800?;increasing the pressure will increase pre-reaction,severely destroying the surface morphology of the BGaN samples.The surface morphology of the BGaN film is the best at a low pressure of 100 mbar;the high B/III ratio will deteriorate the surface morphology of the BGaN films.When the B/III ratio is 10%,the surface morphology of BGaN film is the best.2.Study on the incorporation efficiency of B in BGaN films.Through XRD test,the effect of growth thickness and growth parameters on the B incorporation efficiency in BGaN was studied.The research results show that increasing the film thickness does not change the B incorporation efficiency in BGaN;as the temperature increases,the B component in BGaN increases first and then decreases.At 800?,the B component in the BGaN film is the largest,which is 4.3%;As the pressure increases,the B component in the BGaN film decreases sharply.At a lower pressure of 100 mbar,the B component in the BGaN film is the highest at 4.5%;The boron component increases approximately linearly with the increase of the B/III ratio.When the B/III ratio is 30%,the B component in the BGaN film is the highest,at6.1%.