Epitaxy Growth And Characterization Of Semi-polar Alingan Materials

In recent years,as the preparation technology of blue-green light emitting diode（LED）has been stable and mature,the research on ultraviolet light emitting diode（UV-LED）has gradually entered the view of researchers around the world.The COVID-10 epidemic in early2020 has pushed the research on UV-LED to a climax.Traditional UV-LED were generally prepared by using c-plane Al Ga N-based materials,but there spontaneous-and piezoelectric-polarization induced along the c axis in the c-plane Al Ga N-based materials,leading to significant reduction in carrier recombination,that is the so-called quantum confinement stark effect（QCSE）,and internal quantum efficiency（IQE）will be negatively affected.In addition,due to the difference in Al component of Al Ga N-based material,the lattice constant varies greatly,which results in the large lattice mismatch between hetero-interfaces and brings great negative effects on the crystal quality.For semi-polar（11（?）2）plane Al In Ga N quaternary material,on the one hand,QCSE can be effectively suppressed due to a certain degree of tilt between the direction of the polarization electric field and the growth direction.On the other hand,the lattice constant and band gap of the Al In Ga N material can be adjusted independently by changing the Al and In compositions.In this paper,semi-polar（11（?）2）plane Al In Ga N quaternary materials were grown on non-polar m-plane（101?0）sapphire substrate by metal-organic chemical vapor deposition（MOCVD）technology,and their characteristics were characterized and analyzed systematically.The main research contents and results got in this paper are as follows:1.The semi-polar（11（?）2）plane Al N buffer layer was grown by using ammonia（NH₃）pulse growth method,and the crystal quality and surface morphology of semi-polar（11（?）2）plane Al N buffer layer were effectively improved by optimizing the NH₃ pulse time;Then,the semi-polar（11（?）2）plane Al Ga N epitaxial layer was grown with varied TMAl/TMGa flow ratio and fixed V/III ratio.The effects of the TMAl/TMGa flow ratio on the properties of semi-polar（11（?）2）Al Ga N materials were studied based on systematic characterization results.2.The semi-polar（11（?）2）plane Al In Ga N quaternary material was grown for the first time,and its basic growth mechanism and preparation parameters were analyzed.3.The effect of temperature on the epitaxial growth of semi-polar（11（?）2）plane Al In Ga N quaternary material was studied.Different temperatures were set to grow semi-polar（11（?）2）plane Al In Ga N quaternary material on the prepared semi-polar（11（?）2）plane Al Ga N buffer layers,and It is found that the surface morphology and crystal quality of semi-polar（11（?）2）plane Al In Ga N quaternary material grown at 850°C and 860°C were similar,but the luminescence properties of semi-polar（11（?）2）plane Al In Ga N quaternary material grown at850°C were the best.4.The effects of V/III ratio and TMIn flow rate on the growth process of semi-polar（11（?）2）Al In Ga N quaternary material were compared and analyzed,and then the mechanism was clarified.It was also demonstrated that when the V/III ratio and TMIn flow rate were set at 4681and 7.75 umol/min,respectively,the negative impact of the phase separation effect on the optical characteristic could be significantly suppressed,and the largest near band-edge luminescence intensity for the semi-polar（11（?）2）plane Al In Ga N quaternary material could be achieved.