Effect Of In-Situ Deposited SiN_x Interlayer On GaN Crystal Structure And Morphology

GaN-based semiconductor materials because of its wide band gap,excellent physical and chemical stability,have been widely used in light-emitting diodes?LEDs?,field effect transistors,high-power semiconductor lasers,solar cells and other fields.However,due to the lattice mismatch and thermal mismatch between GaN crystal and sapphire substrate,resulting in the high dislocation density in GaN materials,which affected the crystal quality and photoelectric properties of the semiconductor material.In this paper,we focus on how to improve the GaN crystal quality and morphology.The SiN_x mask layer was grown in situ by metal organic chemical vapor deposition?MOCVD?.High quality GaN epitaxial films and morphologically controlled GaN micro-pyramids were prepared respectively.The effects of Si Nx deposition time,deposition location and different GaN growth modes on the crystal quality and photoelectric properties of GaN epitaxial thin films were studied systematically.At the same time,the effects of growth temperature,growth time,reaction pressure,?/? ratio and the KOH solution corrosion on the morphology of Ga N micro-pyramids structure were investigated,and the mechanism were discussed.Specific results are as follows:The GaN epitaxial films were grown by in situ deposition of SiN_x viaMOCVD.It is demonstrated that the GaN thin films grown on in-situ depsited SiN_x interlayer have lower dislocation density,higher mobility,indicates that SiN_x interlayer can effectively improve the quality of GaN films.The crystal quality of the GaN films grown on SiN_x which deposition time is 120 s are higher than its Si Nx deposition time are 60 s and 180 s.The growth of GaN by two-step after SiN_x deposition leads to the deterioration of crystal quality due to the large number of dislocations in the GaN nucleation layer at low temperature.SiN_x deposition in the nucleation layer after annealing has a lower dislocation density and higher crystal quality due to the reduction of GaN nucleation sites.The GaN micro-pyramids were grown on unintentional doped GaN epitaxial layers with in-situ pre-deposited SiN_x interlayer via MOCVD.The GaN micro-pyramids structure were formed at 1075?.As the growth time was prolonged from 3 min to 20 min,the basal diameter of the GaN micro-pyramids increased from 3.6?m to 19.8?m,while the density decreased from 3.8×10³cm^-2to 0.8×10³cm^-2.The final complete pyramid-like or truncated pyramid-like GaN micro-structures was mainly determined by reaction pressure and V/III ratio.The KOH solution corrodes the sidewalls of the pyramidal GaN-like taper,causing the sidewalls to delaminate.After 20 min of corrosion,the micro-rod-like structure was formed,and its size was related to the topography of the micro-cone.