Epitaxy Of AlGaN/GaN Semiconductor Heterojunctions

AlGaN/GaN Semiconductor Heterojunctions enable a wide range of use in optoelectro-nics, which appeals to a multitude of research work. Thus, lots of experiment work has beencarried out in our research group. In the first part of this thesis, some important physicalprinciples, useful mathematical models and key technology related to semiconductorheterojunction materials and devices have been elaborated on and talked about. The rest ofthis thesis mainly presents the experiment work, which covers the optimization of AlNtemplate, the epitaxy of AlGaN-MQWs based on UV band (~310nm) and some exploratoryexperiment work on AlGaN based distributed Bragg reflector, via tailor-made AlGaN-MOCVD. From our experiments and analyses, a few of conclusions, though some of whichare still under investigation, can be summarized as follows,(1) Enhanced Ammonia and TMA flow rate to reduce V/III ratio appropriately, screwdislocation density in the AlN crystal film template can be effectively inhibited, but theequivalent phenomenon cannot be seen in the case of edge dislocation. In this paper, highquality AlN templates with smooth face, no crack, roughness RMS0.6nm, FWHM of the ωcurve from (002) reflection93.66arcsec, have been synthesized by the reasonableoptimization of growth temperature, Al flux, ammonia flow rate and growth time.(2) AlxGa1-xN/AlyGa1-yN multiple quantum well material with high PL intensity in thewavelength of288nm has been grown, based on the optimized parameters in well layer andbarrier layer growth.Then we fixed the TEG flux in the epitaxy of multiple quantum wellswith varying parameters, such as TMA flux, growth time, satisfactory MQWs can also beobtained. God has instituted the optimum value of the MQWs epitaxial growth, wavelengthdepartures the simulated position can be found in certain rang of growth temperature andgrowth width varies. Besides, all the MQWs heterojunction structures with absorption effectin the transmission spectrum present good performance in PL intensity, which appeals to us.(3) AlxGa1-xN/AlyGa1-yN-Distributed Bragg Reflector(DBR) with high crystal quali-ty, smooth morphology, optical reflection, refraction and light interference phenomenon canbeen systhesised via reasonable Al composition, layer numbers and layer width.