Optical And Electrical Properties Studies Of Different Ions Implanted Gallium Nitride

Gallium Nitride (GaN) is promising wide bandgap material for fabricating high-efficiency light emitting devices in the short-wavelength regions and extremely using devices. It is expected to perform in the radiation environment of military and astronautic domains. In modern device technology, ion implantation is usually employed. In present dessertation, the influence of ion implantation on GaN optical and elctrical properties were investigated; implanted properties of different ions about GaN were also studied; meanwhile, the research on co-implantation effect of GaN in our experiments was started.In this article, Be,Mg,Al,Si ions are used to implant into GaN at room temperature and the fluence range from 10¹³-10¹⁶/cm², Mg+Be and Mg+Si are co-implanted into GaN at room temperature with respective fluence in the range of 10¹³-10¹⁵/cm² and 10¹³-10¹⁶/cm². All the implanted GaN samples were anneald at 950℃for 30 min in a flowing nitrogen environment. Photoluminescence, Raman and electrical properties of different ions implanted GaN were investigated and draw the conclusion as follows:1) The broad yellow luminescence (YL) band ranging from 480 to 700nm was produced by the transition between the energy levels of impurities or defects which was called a shallow donor to deep accepter pair (D_sA_dP) transition. In Be-implanted GaN sample, a different YL mechanism is involved that Be might be expected to form interstitial donors Be_i which is more effective than O_N to stabilize V_Ga and then form complexes V_GaBe_i. The V_GaBe_i can form deep acceptor energy level which is responsible for the YL.2) The theoretical model is developed to deduce the concentration of the defect causing the YL as a function of implanting concentration, are expressed by equation 4.6 and 4.10.3) Co-implantation of Mg and Si results show that for Mg-implanted GaN the blue luminescence (BL) is also a DAP transition, the shallow donor is produced by Mg_i, and the deep acceptor energy level is produced by the complex Mg_GaV_N or an unknown defect which generate deep acceptor state at about 0.43eV above the VB. Meanwhile, the results of co-implantation of Mg and Si support the practice of co-implantation enhance Mg implant activation.4) The experimental results also show that the defect complex such as V_Ga and/or V_Ga-complex is also responsible for the red luminescence (RL); the influence of ion implantation on RL is larger than YL, it means the acceptor energy level responsible for RL is not easy affected by ion implantation.5) Additional Raman peak at 298cm^-1(R1) is attribute to disorder-activated Raman Scattering (DARS), the 667 cm^-1(R3) probably arises from the optical-phonon branch at the zone boundary. The intensity of 360cm^-1 (R2) is dependent on species of implanted ions, fluence and annealing temperature, which is assigned to local vibration of simple defects such as vacancy and interstitial defects, most probable is V_N-related defects.6) The implantation of different ions result in compressive stress of GaN films, compressive stress is almost not dependent on ion fluence; hydrostatic strain is caused by the unit cell expansion/contraction due to: the implantation induced defects such as vacancies and interstitials, and the substitution of host atoms by the implants which have different size than the host lattice atoms, furthermore, the former plays a most crucial role.7) Ion implantation can induce a lots of point defects and simple defect complexes, then form deep traps which capture the electron and/or hole, and result in the increase of resistivity. Acceptor implantation with high fluence will increase resistivity that has practical value.8) When Be ion fluence is 10¹³cm^-2, Be is expected to form interstitial donors Be_i rather than any shallow acceptors.. When Si ion fluence is 10¹⁴cm^-2, self-compensation effects limit the electron density in Si-implanted GaN and induce the increasing resistivity, more fluence could decrease the resistivity.