| With the continuous development of semiconductor materials,the third generation semiconductor materials,represented by III nitride materials,has attracted a great deal of research due to the excellent properties such as wide bandgap,strong polarization,high breakdown field and high electron saturation velocity,meanwhile,they have good thermal stability and chemical stability.Gallium nitride and its alloys are very attractive materials in the past 30 years,especially due to their wide range of applications in electronic and optoelectronic devices.In fact,GaN-related devices,such as high-brightness light emitting diodes,blue laser diodes,high frequency and high power electronics devices have achieved great successes.However,the development of gallium nitride based optoelectronic devices has been limited by the difficulty of p-type with high conductivity.In addition,compared with the Ga surface GaN materials,use N-face,non-polar and semi-polar GaN materials have huge potential advantage in both electronic device and optoelectronic device.But GaN films of these planes using MOCVD epitaxial growth would induce high dislocation density and high background impurities,which degenerate device performance and limit the application of devices.Therefore,it is necessary to understand how the point defects affect the electrical performance and luminescence properties of GaN based device.In this article,the method for the preparation of Mg-doped p-GaN with high conductivity is studied.Furthermore,the effects of carbon acceptor impurities in GaN materials on the electrical properties and luminescence properties are investigated.Firstly,we propose a method for the preparation of high conductivity p-GaN by using Mg ?-doped at the Al GaN/GaN superlattice interface.The three different doping p-type GaN was realized by using uniform doping,?-doping and ?-doping at the Al GaN/GaN superlattice interface.At room temperature,the contact Hall results show that the method of ?-doping at the Al GaN/GaN superlattice interface increases the hole concentration in GaN material by nearly twice as much as the uniform doping sample,and the resistance is reduced by 1/3.APSYS software is used to simulate the energy band in this optimization doping mode,and the mechanism of increasing the ionization rate of Mg is explained.Secondly,a method to reduce the high background carrier concentration by implanted C as accepter impurity in GaN film is proposed.In this part,C-implanted N-face,non-polar and semi-polar(11-22)GaN samples are investigated.After C-implantation,high temperature annealing process is use to recover GaN lattice,which is identified by the Raman results.Cimplantation can induce deep acceptor in GaN,so the background carriers induced by the high oxygen incorporation in the N-polar GaN film will be compensated partially,resulting in a 25 times higher resistivity,which is demonstrated by temperature-dependent Hall-effect measurement.The problem of high background carrier in N-face GaN caused by O impurities can be effectively solved,so the high-resistance N-face GaN material can be obtained by introducing carbon acceptor impurity.Finally,the mechanism of yellow band luminescence in GaN materials is investigated.Nface,non-polar and semi-polar(11-22)GaN samples implanted with C or O ion are studied.The results of PL spectrum indicate that C-implanted samples had obvious increase in the yellow luminescence while the O-implanted samples showed only a slight increase.It can be concluded that gallium vacancy and related complex defects were not the major factor for YL.The present result confirmed that the C and related complex defects are responsible for the increased YL intensities in GaN.The luminescence properties of ELOG GaN in cross section are investigated,PL results showed a positive correlation between the C impurity concentration and yellow luminescence intensities,further verified the relationship between C impurity and the yellow luminescence in GaN. |
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