Characterizations of Mg Implanted GaN
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027 Mat. Res. Soc. Symp. Proc. Vol. 482 ©1998 Materials Research Society
525°C [2]. Mg + ions were implanted at a dose of 5 x 1013 cm- 2 at energy of 150KeV. Post-implant annealing at 700'C and 1000°C for 15 seconds was performed in N2 ambient by RTA, without an encapsulation layer. The photoluminescence was excited by the focused beam of a He-Cd 325nm laser with laser power of several milliwatts. The sample was mounted on the cold finger of a closed-cycle liquid-helium cryostat. The x-ray diffraction experiment was performed using a high resolution setup of x-ray diffractometer which includes, mainly, an 18KW rotating anode x-ray generator. In this experiment, a Ge(l 11) monochromator and 200 pam precision slit was used to define the Cu K3(X=0. 13922nm). A distance of 770mm from the sample to the x-ray detector was used to eliminate the parasitic-scattering photons. In the final setup, an incidence beam divergence of 50 arc seconds(FWHM) at the sample position and spatial resolution of 0.04 degree at the direct beam was achieved, which was capable of measuring a sample with coherence length of more than 100nm. The orientation relation between the epitaxial film and the substrate was measured by using the methods of (1) traditional 0/20 scan normal to the epitaxial plane to see the crystalline size and microstrain along the plane normal direction (2) 0 rocking curve to observe the spread of mosaic structure of GaN (3) grazing incidence x-ray to see the quality of the in-plane structure. RESULTS AND DISCUSSIONS Figure 1 shows the photoluminescence of as-grown GaN at 20K. The dominant narrow peak at 358nm is attributed to the radiative recombination of bound excitons [3-5]. The yellow luminescence might be from a defect [5]. Figure 2 shows the temperature dependence of the photoluminescence of the Mg-implanted GaN annealed at 1000*C. The peak at 378nm is attributed to the Donor-Acceptor (D-A) band of as-grown GaN and followed by a series of LO phonon replicas [5-6]. The positions of these peaks are independent of temperature. These peaks disappear above 130K. The green band photoluminescence of the Mg-implanted GaN disappears above 200K. The temperature dependence of the photoluminescence of Mg-implanted GaN annealed at 700°C is shown in figure 3. The D-A band at 378nm is not observed. There are violet and green band photoluminescence from Mg-implanted GaN annealed at 700°C. The violet band photoluminescence disappears above 130K and the green band photoluminescence disappears above 200K. The violet band emission of Mg-implanted GaN annealed at 700'C has similar temperature dependence with the D-A emission. The emission mechanism of this violet band photoluminescence might be similar with D-A emission. The green band photoluminescence of Mg-implanted GaN annealed at 700 0 C and 1000°C have been associated with Mg-induced defect clustering in GaN [7]. In summary, the photoluminescence of Mg-implanted GaN annealed by
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RTA displays green luminescence at low temperature. It is different from Mg-doped GaN grown by
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