The Influence Of Vicinal Sapphire Substrate On ?-nitride Material Epilayers

Ga N is excellent third generation wide bandgap semiconductor material,Ga N-based materials have a very broad applications in the field of electronic devices and optoelectronic devices.The light emitting wavelength of Ga N-based light-emitting diodes(LEDs)can cover the near-infrared band to the ultraviolet band,so Ga N-based LEDs have a large number of applications in the field of white lighting,ultraviolet,green light.However,due to the heteroepitaxy growth of III-nitride materials,there is large lattice and thermal mismatch between the material and the substrate,resulting in a large number of dislocations in Ga N-based materials.These dislocations are non-radiative recombination centers,which can reduce the LED's emitting efficiency.In order to solve the above problems and improve the crystallization quality of III-nitride materials,we studied the III-nitride materials grown on the vicinal sapphire substrate at c toward m orientation(c/m for short).The main research contents and results are as follows:First,we studied the effect of vicinal substrate on the crystal quality of Al N.The 300nm thick Al N samples were magnetron sputtering on c/m 0°,c/m 1°and c/m 4°vicinal sapphire substrates,and the samples were annealed in nitrogen atmosphere at1000?,1100?and without annealed.The test results show that the increase of vicinal angle is beneficial to the decrease of dislocation density in the sample,and can effectively improve the crystal quality of the samples.The c/m 4°AlN sample treated by annealing at 1000? is the best situation.The full-width at half-maximum(FWHM)for the(002)plane of the high-resolution X-ray diffraction(HRXRD)rocking curve is 345.24 arcsec and the FWHM for(102) plane is 3595.32 arcsec.The surface is relatively smooth and the roughness is 1.33nm.Secondly,we studied the effect of different angle vicinal substrates on LED material quality.LED structures were grown on vinical sapphire substrates with c/m 0°,c/m 1°,c/m 2°,c/m 3°,c/m 4°,c/m 5°,and c/m 6°,respectively.The samples of vicinal LED were tested and characterized by HRXRD,atomic force microscopy(AFM),Raman spectroscopy(Raman),and photoluminescence(PL).The test results showed that the vicinal substrate can improve the crystal quality of the sample obviously,and the dislocation density is reduced with the angle of vicinal substrate increasing.The sample of c/m 5°is the optimal situation,the FWHM of(002) plane is 219.6 arcsec,the FWHM of(102)plane is 262.08 arcsec,and the dislocation density in the sample is 4.61×10⁸cm^-2,which is reduced to 10% of the dislocation density in the c-plane sample.The surface of the sample is rough,and the morphology with large grains is characterized by 3D growth mode.With the increase of the vicinal angle of the sample,the compressive stress in the sample increases gradually.The PL luminescence peak of the sample is generally redshifted.As the vicinal angle increases,due to the lateral epitaxy process enhanced,the large grains on the surface merge each other,the boundary of the independent large grains become blurred,and the surface fluctuation decreases.Finally,we studied the effect of different vicinal angle substrates on LED material quality after introducing magnetron sputtering Al N nucleation layer.We grew the Al N nucleation layer by magnetron sputtering on the vicinal sapphire substrate with c/m 0°,c/m 1°,c/m 2°,c/m 3°,c/m 4°,c/m 5°and c/m 6°respectively,then grew the LED structure,and tested and characterized the sample of the vicinal LED.The test results showed that the crystal quality of the sample was improved by introducing vicinal substrate,with the increase of the vicinal angle,the improvement effect becomes more obvious.However,when the vicinal angle is larger than c/m 4°,the dislocation density in the sample decreases by a minimum.The introduction of magnetron sputtering Al N nucleation layer can also improve the crystal quality of samples.The sample of c/m 4°is the optimal situation,the FWHM of(002)plane is 89.28 arcsec,the FWHM of(102) plane is281.52 arcsec and the dislocation density in the sample is 4.36×10⁸cm^-2,with the best improvement effect.A smooth surface with a roughness RMS of 12.1nm was obtained.