Ultra-high implant activation efficiency in GaN using novel high temperature RTP system (original) (raw)
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Rapid Thermal Processing of Implanted GaN Up to 1500 C
1999
GaN implanted with donor(Si, S, Se, Te) or acceptor (Be, Mg, C) species was annealed at 900-1500 °C using AlN encapsulation. No redistribution was measured by SIMS for any of the dopants and effective diffusion coefficients are ≤2×10-13 cm 2 ⋅ s-1 at 1400 °C, except Be, which displays damage-enhanced diffusion at 900 °C and is immobile once the point defect concentration is removed. Activation efficiency of ~90% is obtained for Si at 1400 °C. TEM of the implanted material shows a strong reduction in lattice disorder at 1400-1500 °C compared to previous results at 1100 °C. There is minimal interaction of the sputtered AlN with GaN under our conditions, and it is readily removed selectively with KOH.
Applied Physics Letters, 2004
Activation annealing of Si implants in metalorganic-chemical-vapor-deposition-grown GaN has been studied for use in ohmic contacts. Si was implanted in semi-insulating GaN at 100 keV with doses from 5 ϫ 10 14 to 1.5ϫ 10 16 cm −2. Rapid thermal annealing at ϳ1500°C with 100 bar N 2 overpressure was used for dopant activation, resulting in a minimum sheet resistance of 13.9 ⍀ / square for a dose of 7 ϫ 10 15 cm −2. Secondary-ion-mass-spectroscopy measurements showed a post-activation broadening of the dopant concentration peak by 20 nm (at half the maximum), while x-ray triple-axis-2 scans indicated nearly complete implant damage recovery. Transfer-length-method measurements of the resistance of Ti/ Al/ Ni/ Au contacts to activated GaN:Si (5 ϫ 10 15 cm −2 at 100 keV) indicated contact resistances of 0.07 and 0.02 ⍀ mm for as-deposited and subsequently annealed contacts, respectively.
High temperature annealing of Er implanted GaN
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2001
Defect recovery, optical activation and diffusion of Er implanted GaN epilayers grown on sapphire were studied after annealing at 1000°C with proximity cap and 1200°C under nitrogen atmosphere at high pressure (1GPa). The erbium ions with 160 keV were implanted at room temperature to nominal fluences of 5 × 10 14 cm − 2 and 5× 10 15 cm − 2 . Some samples were co-implanted with oxygen ions to study its influence on the Er behaviour. During implantation a large fraction of Er is incorporated in Ga sites of the GaN lattice for the samples implanted with lower dose. The implantation damage recovers almost completely after rapid thermal annealing (120 s) at 1000°C with proximity cap. The annealing has no influence on the Er profile. The increase of the annealing time leads to the degradation of the surface due to nitrogen loss. The samples implanted with higher fluence and exposed to the same annealing procedure display distinct behaviour depending on the presence of oxygen. In samples without oxygen, the recovery is faster and accompanied by the segregation of Er towards the surface. For samples containing oxygen the damage recovery proceeds slowly and the Er profile remains stable. Annealing at 1200°C in nitrogen atmosphere at a pressure of 1GPa promotes the complete recovery of the damage in the sample without oxygen. During this annealing, a fraction of Er diffuses into the bulk. After annealing the optical spectra reveal the presence of several sharp lines the intensity of which increases significantly with the annihilation of the implantation damage. : S 0 9 2 1 -5 1 0 7 ( 0 0 ) 0 0 6 9 0 -5
High Temperature Implantation of Tm in GaN
MRS Proceedings, 2003
Thulium ions were implanted into MOCVD grown GaN films with a fluence of 2.5×10 15 at/cm 2 at temperatures between 20 and 500 °C. The lattice damage introduced by the implantation and the effect of post-implant annealing were investigated using the Rutherford backscattering/channeling (RBS/C) technique. Whereas for room temperature implantation the implanted layer becomes amorphous, high temperature implantation inhibits amorphisation. For implantation temperatures higher than 300 °C the RBS/C results clearly show two different damage regions -one at the surface and the second deeper in the crystal coinciding with the Tm depth profile. Annealing causes a decrease of the surface damage as well as initiating regrowth from the unimplanted bulk GaN. For the samples that were not completely amorphous a large part of the Tm atoms were found to be incorporated in Ga-sites. The optical properties of the ion implanted GaN films have been studied by room temperature cathodoluminescence. Directly following the implantation no Tm-related luminescence was observed. Subsequent annealing of the samples achieved optical activation, revealing well-defined emissions due to intra-4f-shell transitions of the Tm 3+ ions in the blue spectral range at 477 nm and in the near infra-red at 804 nm.
Symmetric Multicycle Rapid Thermal Annealing: Enhanced Activation of Implanted Dopants in GaN
ECS Journal of Solid State Science and Technology, 2015
Selectively activated p-type regions are necessary for many electronic devices that require planar processing. The standard process of implanting p-type dopants, such as Mg, in GaN is notoriously more difficult than in other material systems, as the extremely high temperatures required to activate the implanted Mg also damage the GaN surface. In this research, a novel annealing technique is introduced for this purpose-symmetric multicycle rapid thermal annealing (SMRTA). It is shown that SMRTA is superior to the earlier developed multicycle rapid thermal annealing (MRTA) in terms of improvement of the crystalline quality of implanted GaN. The SMRTA technique was applied to Mg-implanted GaN to realize a rectifying junction. The annealing process detailed in this research will be a key enabling step for future GaN-based devices that require planar processing with selective area implants.
Improvements in the Annealing of Mg Ion Implanted GaN and Related Devices
IEEE Transactions on Semiconductor Manufacturing, 2016
The activation of ion implanted p-type dopants in GaN is notoriously difficult as the extremely high temperatures required to activate implanted Mg also damage the GaN crystal. In this paper, we present refinements to our novel annealing process (symmetric multicycle rapid thermal annealing) to reduce surface damage and contamination responsible for elevated leakage currents and non-ideal diode behavior. Furthermore, we apply the technique to Mg-implanted bulk GaN substrates to enable vertical power device structures, demonstrating rectifying p-in junctions. In addition, the technique was applied for edge termination in both p-in and Schottky barrier diodes, realizing floating guard ring and junction termination extension structures. The processes demonstrated here represents a key enabling step for future GaN-based power devices.
Reduced Contact Resistance in GaN Using Selective Area Si Ion Implantation
IEEE Transactions on Semiconductor Manufacturing, 2019
We report selective area n-type doping using ion implantation of Si ions into semi-insulating, C-doped GaN samples activated using both conventional rapid thermal annealing (RTA) and 30 atm N2 overpressure annealing. Implanted regions were tested for Si activation using Circular Transmission Line Measurements (CTLM), while linear and circular photoconductive switches (PCSS) in the unimplanted regions were used as a test vehicle to separate implanted Si dopant activation from leakage paths generated by N vacancy formation due to damage and decomposition during annealing. We observed that at an optimal temperature around 1060°C, a low contact resistivity of 1x10-6 -cm 2 was observed while preserving the breakdown of the unimplanted regions.
GaN evaporation and enhanced diffusion of Ar during high-temperature ion implantation
Journal of Applied Physics, 2003
GaN films were implanted with 150 keV Ar ϩ at temperatures up to 1100°C to a dose of 3 ϫ10 15 cm Ϫ2 . Concentration profiles of Ar were measured by secondary ion mass spectroscopy and depth distributions of ion-induced damage were estimated from Rutherford backscattering/ channeling spectra. No redistribution of Ar atoms was detected up to 700°C. At 1000°C a deep penetrating diffusion tail and a shift of the Ar peak to the surface were observed. At temperatures higher than 800°C shift of the damage peak to the surface was also observed. We attributed the shift of the Ar peak and the damage peaks to evaporation of thin layer of GaN during high-temperature implantation and estimated its temperature dependence.
High-temperature annealing and optical activation of Eu-implanted GaN
Applied Physics Letters, 2004
Europium was implanted into GaN through a 10 nm thick epitaxially grown AlN layer that protects the GaN surface during the implantation and also serves as a capping layer during the subsequent furnace annealing. Employing this AlN layer prevents the formation of an amorphous surface layer during the implantation. Furthermore, no dissociation of the crystal was observed by Rutherford backscattering and channeling measurements for annealing temperatures up to 1300°C. Remarkably, the intensity of the Eu related luminescence, as measured by cathodoluminescence at room temperature, increases by one order of magnitude within the studied annealing range between 1100 and 1300°C.