Study Of Defects In AlInN Epilayers And The Effect On Optical And Electrical Properties

High quality AlInN, lattice-matched to GaN, has been widely used inoptoelectronic and microelectronic devices because of its excellent properties. Sincethe band gap of Al_1-xIn_xN can be adjusted between0.7eV and6.2eV, it can realizethe emission and detection of wavelength rang from ultraviolet to infrared. In addition,the large difference between its refractive indexes and that of GaN, low residual stress,strong spontaneous polarization, high stability and other advantages make AlInN as apotentially promising material use for semiconductor devices such as distributedBragg reflectors （DBR）, high electron mobility transistors （HEMT）, ultraviolet lightemitting diodes （LED） and detectors.In this thesis, we have studied the influence of reactor pressure and V/III ratio onthe growth mode, crystal quality and of AlInN epilayers grown by metalorganicchemical vapor deposition （MOCVD）. The experimental results suggest that crystalquality of the epilayers deteriorates with the increase of ammonia flow rate, while noobvious changes of the surface morphology are observed. When the reactor pressurewas increased from60torr to80torr, the growth mode of AlInN epilayers shifts fromStranski-Krastanov to Volmer-Weber with distinct change of the surface morphology,and the indium incorporation efficiency is reduced.The V-defects in AlInN epilayers, phase separation and unintentionally doped Gaatoms are studied intensively by the transmission electron microscopy （TEM） and thesecondary ion mass spectroscopy （SIMS）.The results show that one part of theV-defects originates from the threading dislocations, while the other part of V-defects originates in AlInN epilayers which is not connected with any threading dislocations.The V-defects also greatly affect the indium incorporation efficiency. Theexperimental results indicate that there exists an obvious in-plane phase separation inAlInN epilayers with a gradient distribution of the components along the growthdirection. In addition, a large number of unintentionally incorporated Ga atoms havebeen found in the AlInN epilayers. The underlying GaN template has been found tobe the main source supplying most of the unexpected Ga atoms during epitaxialgrowth, by the path of atom interdiffusion between In, Al, and Ga atomsincorporating into the AlInN epilayers. Finally, the optical and electrical properties ofthe AlInN epilayers are investigated employing cathodoluminescence（CL） and Halltest.