Structural properties of ne implanted GaN

We report a study on the micro-structural changes in GaN due to neon ion implantation using the x-ray diffraction and Raman scattering techniques. An implantation dose of 10(14) cm(-2) was found unable to produce lattice deformation observable by Raman measurements. For higher doses of implantation several disorder activated Raman scattering centers were observed which corroborate the literature. A new dose dependent feature has been recorded at 1595 cm(-1) for higher implantation doses which is suggested to be the vibrational mode of microcavities produced in the lattice.

Effect of annealing on photoluminescence properties of neon implanted GaN

The effect of thermal annealing on the luminescence properties of neon implanted GaN thin films was studied. Low temperature photoluminescence (PL) measurements were carried out on the samples implanted with different doses ranging from 10(14) to 9 x 10(15) cm(-2) and annealed isochronally at 800 and 900 degrees C. We observed a new peak appearing at 3.44 eV in the low temperative PL spectra of all the implanted samples after annealing at 900 degrees C. This peak has not been observed in the PL spectra of implanted samples annealed at 800 degrees C except for the samples implanted with the highest dose. The intensity of the yellow luminescence (YL) band noticed in the PL spectra measured after annealing was observed to decrease with the increase in dose until it was completely suppressed at a dose of 5 x 10(15) cm(-2). The appearance of a new peak at 3.44 eV and dose dependent suppression of the YL band are attributed to the dissociation of VGaON complexes caused by high energy ion implantation.

Structural and Magnetic Properties of Sm Implanted GaN

The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering temperature above room temperature in all the implanted samples, while the effective magnetic moment per Sm obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94(2005) 037205, Phys. Rev. B 72(2005) 245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms.

Study of infrared luminescence from Er-implanted GaN films

In this study, we report the dependences of infrared luminescence properties of Er-implanted GaN thin films (GaN:Er) on the kinds of substrates used to grow GaN, the growth techniques of GaN, the implantation parameters and annealing procedures. The experimental results showed that the photoluminescence (PL) intensity at 1.54 mum was severely influenced by different kinds of substrates. The integrated PL peak intensity from GaN:Er /Al2O3 (00001) was three and five times stronger than that from GaN:Er /Si (111) grown by molecular beam epitaxy (MBE) and by metalorganic chemical vapor deposition (MOCVD), respectively. The PL spectra observed from GaN:Er/Al2O3 (0001) grown by MOCVD and by MBE displayed a similar feature, but those samples grown by MOCVD exhibited a stronger 1.54 mum PL. It was also found that there was a strong correlation between the PL intensity with ion implantation parameters and annealing procedures. Ion implantation induced damage in host material could be only partly recovered by an appropriate annealing temperature procedure. The thermal quenching of PL from 15 to 300 K was also estimated. In comparison with the integrated PL intensity at 15 K, it is reduced by only about 30 % when going up to 300 K for GaN:Er/Al2O3 sample grown by MOCVD. Our results also show that the strongest PL intensity comes from GaN:Er grown on Al2O3 substrate by MOCVD. (C) 2004 Elsevier B.V. All rights reserved.

Structure and photoluminescence studies of Pr-implanted GaN

The structure and photoluminscence (PL) properties of Pr-implanted GaN thin films have been studied. RBS/channeling technique was used to explore the damage recovery at high annealing temperature and study the dependence of the radiation damage with ion implantation direction. A complete recovery of the ion implantation damage cannot be achieved at annealing temperatures up to 1050degreesC. It is found that the channeling implantation results in the decrease of the damage. The PL experimental results indicate that the PL efficiency increases exponentially with annealing temperature up to the maximum temperature of 1050degreesC. Moreover, the PL intensity is also seriously affected by ion implantation geometries. The PL intensity for the sample implanted along channeled direction is nearly 2 times more intense than that observed from the sample implanted along random direction. The thermal quenching of PL intensity from 10 to 300K for sample annealed at 1050degreesC is only 30%. (C) 2004 Elsevier B.V. All rights reserved.

Photoluminescence study on Eu-implanted GaN

The photoluminescence (PL) properties of Eu-implanted GaN thin films are studied. The experimental results show that the PL intensity is seriously affected by ion implantation conditions. The PL efficiency increases exponentially with annealing temperature increasing up to a maximum temperature of 1050 degrees C. Moreover, the PL intensity for the sample implanted along the channelling direction is nearly twice more than that observed from the sample implanted along the random direction. The thermal quenching of PL intensity from 10K to 300K for sample annealed at 1050 degrees C is only 42.7%.

Electrical characterization of Er- and Pr-implanted GaN films

Hall, current-voltage, and deep-level transient spectroscopy measurements were used to characterize the electrical properties of metalorganic chemical vapor deposition grown undoped, Er- and Pr-implanted GaN films. Only one deep level located at 0.270 eV below the conduction band was found in the as-grown GaN films. However, four defect levels located at 0.300, 0.188, 0.600, and 0.410 eV below the conduction band were found in the Er-implanted GaN films after annealing at 900 degrees C for 30 min, and four defect levels located at 0.280, 0.190, 0.610, and 0.390 eV below the conduction band were found in the Pr-implanted GaN films after annealing at 1050 degrees C for 30 min. The origins of the deep defect levels are discussed. (C) 2005 American Institute of Physics.

PIXE analysis of Fe content in Fe-implanted GaN film

The diluted magnetic semiconductors (DMSs) were achieved by the ion implantation. Fe+ ions (250 keV) were implanted into n-type GaN at room temperature with doses ranging from 8 X 10(15) cm(-2) to 8 X 10(16) cm(-2) and subsequently rapidly annealed at 800 degrees C for 5 m in N-2 ambient. PIXE was employed to determine the Fe-implanted content. The magnetic property was measured by the Quantum Design MPMS SQUID magnetometer. No secondary phases or clusters are detected within the sensitivity of XRD. Apparent ferromagnetic hysteresis loops measured at 10 K were presented. The relationships between the Fe-implanted content and the ferromagnetic property are discussed. (c) 2006 Elsevier B.V. All rights reserved.

Deep level and photoluminescence studies of Er-implanted GaN films

Deep level transient spectroscopy measurements were performed on the metal organic chemical vapor deposition epitaxially grown GaN before and after the implantation with Er. Only one deep level located at 0.270 eV below the conduction band was found in the as-grown GaN films. But four defect levels located at 0.300, 0.188, 0.600 and 0.410 eV below the conduction band were found in the Er-implanted GaN films after annealing at 900 degrees for 30 min. The origins of the deep defect levels were discussed. The photoluminescence (PL) properties of Er-implanted GaN thin films were also studied. After annealing at 900 degrees for 30 min in a nitrogen flow, Er-related 1.54 mu m luminescence peaks could be observed for the Er-implanted GaN sample. Moreover, the energy-transfer and recombination processes of the Er-implanted GaN film were described. (c) 2006 Elsevier B.V. All rights reserved.

Deep level transient spectroscopy studies of Er and Pr implanted GaN films

Deep level transient spectroscopy measurements were used to characterize the electrical properties of metal organic chemical vapor deposition grown undoped, Er-implanted and Pr-implanted GaN films. Only one deep level located at 0.270 eV below the conduction band was found in the as-grown GaN films. But four defect levels located at 0.300 eV, 0.188 eV, 0.600 eV and 0.410 eV below the conduction band were found in the Er-implanted GaN films after annealing at 900 degrees C for 30 min, and four defect levels located at 0.280 eV, 0.190 eV, 0.610 eV and 0.390 eV below the conduction band were found in the Pr-implanted GaN films after annealing at 1050 degrees C for 30min. The origins of the deep defect levels are discussed. After annealing at 900 degrees C for 30min in a nitrogen flow, Er-related 1538nm luminescence peaks could be observed for the Er-implanted GaN sample. The energy-transfer and luminescence mechanism of the Er-implanted GaN film are described.

RBS/channeling study and photoluminscence properties of Er-implanted GaN

The Raman back scattering/channeling technique was used to analyze the damage recovery at different annealing temperatures and to determine the lattice location of the Er-implanted GaN samples. A better damage recovery was observed with increasing annealing temperature below 1000degreesC, but a complete recovery of the implantation damage cannot be achieved. For a sample annealed for at 900degreesC 30 min the Er and Ga angular scans across the <0001> axis was measured indicating that about 76% of Er ions occupies substitutional sites. Moreover, the photoluminscence (PL) properties of Er-implanted GaN thin films have been also studied. The experimental results indicate that those samples annealed at a higher temperature below 1000degreesC had a stronger 1539nm PL intensity. The thermal quenching of PL intensity for samples annealed at 900degreesC measured at temperatures from 15K to 300K is 30%.

Hydrogen-decorated lattice defects in proton implanted GaN

Several vibrational bands were observed near 3100 cm(-1) in GaN that had been implanted with hydrogen at room temperature and subsequently annealed, Our results indicate that these bands are due to nitrogen-dangling-bond defects created by the implantation that an decorated by hydrogen, The frequencies are close to those predicted recently for V-Ga-H-n complexes, leading us to tentatively assign the new lines to V-Ga defects decorated with different numbers of H atoms. (C) 1998 American Institute of Physics. [S0003-6951(98)03614-6].

Study of infrared luminescence from Er-implanted GaN films

In this study, we report the dependences of infrared luminescence properties of Er-implanted GaN thin films (GaN:Er) on the kinds of substrates used to grow GaN, the growth techniques of GaN, the implantation parameters and annealing procedures. The experimental results showed that the photoluminescence (PL) intensity at 1.54 mum was severely influenced by different kinds of substrates. The integrated PL peak intensity from GaN:Er /Al2O3 (00001) was three and five times stronger than that from GaN:Er /Si (111) grown by molecular beam epitaxy (MBE) and by metalorganic chemical vapor deposition (MOCVD), respectively. The PL spectra observed from GaN:Er/Al2O3 (0001) grown by MOCVD and by MBE displayed a similar feature, but those samples grown by MOCVD exhibited a stronger 1.54 mum PL. It was also found that there was a strong correlation between the PL intensity with ion implantation parameters and annealing procedures. Ion implantation induced damage in host material could be only partly recovered by an appropriate annealing temperature procedure. The thermal quenching of PL from 15 to 300 K was also estimated. In comparison with the integrated PL intensity at 15 K, it is reduced by only about 30 % when going up to 300 K for GaN:Er/Al2O3 sample grown by MOCVD. Our results also show that the strongest PL intensity comes from GaN:Er grown on Al2O3 substrate by MOCVD. (C) 2004 Elsevier B.V. All rights reserved.

Ferromagnetic modification of GaN film by Cu+ ions implantation

The structural and magnetic properties of Cu+ ions-implanted GaN films have been reported. Eighty kilo-electron-volt Cu+ ions were implanted into n-type GaN film at room temperature with fluences ranging from 1 x 10(16) to 8 x 10(16) cm(-2) and subsequently annealed at 800 degrees C for 1 h in N-2 ambient. PIXE was employed to determine the Cu-implanted content. The magnetic property was measured by the Quantum Design MPMS SQUID magnetometer. No secondary phases or clusters were detected within the sensitivity of XRD. Raman spectrum measurement showed that the Cu ions incorporated into the crystal lattice positions of GaN through substitution of Ga atoms. Apparent ferromagnetic hysteresis loops measured at 10 K were presented. The experimental result showed that the ferromagnetic signal strongly increased with Cu-implanted fluence from 1 x 10(16) to 8 x 10(16) cm(-2).

Dependence of implantation-induced damage with photoluminescence intensity in GaN : Er

Erbium was implanted with energies 200 or 400 keV into epitaxial (0 0 0 1) GaN grown on (0 0 0 1) Al2O3 substrate at room temperature (RT) and 400degreesC. Both random (10degrees tilt from c-axis) and channeled (along c-axis) implantations were studied. RBS/Channeling technique was used to study the dependences of the radiation damage with ion implantation energy, direction and temperature. It was found that the channeling implantation or elevating temperature implantation both resulted in the decrease of the damage. Moreover, the Photoluminscence (PL) properties of Er-implanted GaN thin filius were also studied. The experimental results indicate that the PL intensity can be enhanced by raising implantation energy or implanting along channeling direction. (C) 2004 Elsevier B.V. All rights reserved.