Growth And Property Of AlInGaN Films And GaN-Based DBRs

Ⅲ-nitrides(GaN,AlN and InN) have been attracting a great deal of attention and research due to their outstanding optical and electrical properties.All quaternary AlInGaN alloys with arbitrary element contents are direct optical bandgaps,which can be used in high efficiency light-emitting and electronic devices.Nowadays,quaternary AlInGaN alloys are becoming a new study hotspot after their ternary alloy systems. On the other hand,GaN-based vertical cavity surface emitting laser(VCSEL) is always the frontier topic ofⅢ-nitrides.Therefore, high-reflectivity distributed Bragg reflector(DBR),as an important component in VCSEL,has also been widely studied.In this paper,we focus on preparation and characterization of quaternary AlInGaN films and GaN-based DBRs grown on C-plane sapphire by metal organic chemical vapor deposition(MOCVD).The main results are summarized as follows:1.Growth characteristics of quaternary AlInGaN films are investigated in details.It is found that growth temperature has significant influence on the surface morphology.We confirm that the composition pulling effect occurs in AlInGaN films.We also observe strong dependence of composition in AlInGaN films on the reactor pressure.2.It is demonstrated that low temperature(LT) AlN insertion layer between GaN buffer layer and AlInGaN epilayer can affect strain distribution and improve the surface morphology.3.The growth mechanism of AlInGaN at different temperatures is studied.By controlling the growth temperature,a-plane lattice-matched AlInGaN/GaN heterostructure is obtained.4.Based on geometrical optics theory,the influence of refractive index,period number and thickness deviation on reflective spectra is simulated.AlInGaN/GaN DBRs are fabricated on GaN/Sapphire templates,and the influence of growth temperature and GaN buffer layer on the performance of DBR is investigated5.High reflectivity AlN/GaN DBRs are grown on GaN/sapphire templates by MOCVD.By controlling the thickness of GaN buffer layer,inserting LT-AlN layer and doping Indium during the growth of theλ/4 AlN layers, the magnitude of strain in DBR is reduced and the surface morphology of the sample is improved.The peak reflectivity of two DBRs attains to 99% in violet and blue regions,respectively.