MOCVD Epitaxial Growth And Characterization Of Polar AlGaN Materials And Related Quantum Structures

As one of the third-generation semiconductor materials,AlGaN material has a very broad application prospect in the field of optoelectronic devices such as deep ultraviolet light-emitting diodes(DUV-LEDs).At present,most of the AlGaN-based UV-LEDs are polar materials grown on c(0001)plane sapphire substrates.For polar AlGaN-based UV-LEDs,although quantum confined Stark effect(QCSE)exists in the AlGaN material,which can be compensated by improving the crystalline quality of the AlGaN material,optimizing the n-and p-type doped layers and the quantum structure,and improving the UV-LED device process technology.In this thesis,the metal organic chemical vapor deposition(MOCVD)technology was used to successfully fabricate the full structure of the DUV-LED with an emission wavelength of 275 nm.And a Mg-doped composite last quantum barrier(CLQB)was introduced.The impact of the introduction of the CLQB and the influence of the Mg doping on the light output power of DUV-LEDs have been studied,and the light output power of DUV-LEDs has been increased by nearly 30% with optimal Mg doping.The main research contents and results achieved in this study are as follows:1.The optimization of the growth process for the HT-AlN buffer layer were described in detail.And by optimizing the growth temperature and the ?/? ratio of the HT-AlN buffer layer,a buffer layer with significantly improved crystalline quality and surface morphology was successfully prepared,which provides the foundation for growing whole structure of the DUVLED.2.Based on the HT-AlN buffer layer,the MOCVD technology was used to successfully fabricate the u-doped AlN/Al0.55Ga0.45 N SL structure used as a stress relief and dislocation filter layer to reduce the stress and threading dislocations density in the epitaxial layer.And the full structure of DUV-LED with traditional u-LQB with a luminous wavelength of 275 nm was successfully fabricated.In addition,p-CLQB was introduced innovatively,and the influence of the introduction of p-CLQB on the light output power of DUV-LED was deeply studied.It was found that p-CLQB with an appropriate amount of Mg doping level is beneficial to increase the light output power of DUV-LEDs,but excessive Mg doping will cause a surge in the number of impurity-related defects,resulting in sub-band parasitic luminescence,leading to the decrease of output power.3.In addition of the introduction of the CLQB,the amount of the doped Mg in the CLQB was also optimized.And the photoluminescence(PL)spectroscopy,electroluminescence(EL)spectroscopy and other characterization methods were employed to study the effect of the Mg doping on the light output power of the DUV-LED.The DUV-LED with enhanced light output power was successfully fabricated under the optimal Mg doping level.In fact,the light output power of the AlGaN-based DUV-LED with the optimized CLQB was increased by approximately 30% as compared with the DUV-LEDs fabricated without the insertion of the pCLQB at an injection current of 40 m A.