Compositional dependence of damage buildup in Ar-ion bombarded AlGaN K. Pągowska 1, R. Ratajczak 1,...
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Compositional dependence of damage buildup in Ar-ion bombarded AlGaN K. Pągowska 1 , R. Ratajczak 1 , A. Stonert 1 , L. Nowicki 1 and A. Turos 1,2 1 Soltan Institute for Nuclear Studies, 05-400 Świerk/Otwock, Poland 2 Institute of Electronic Materials Technology, Wólczyńska 01-919 Warsaw, Poland channelnum ber 100 200 300 400 500 600 700 800 yield (counts) 0 500 1000 1500 2000 2500 3000 random virgin 5E14 2E15 5E15 1E17 SAMPLE PREPARATION GaN, Al 0.4 Ga 0.6 N and AlN layers of 1 μm thickness were grown on sapphire substrates using the MOVPE technique. Epitaxial layers were bombarded with 320 keV Ar ions to fluence ranging from 5х10 12 to 1х10 17 /cm 2 at RT. EXPERIMENTAL RBS/channeling with 1.70 MeV 4 He-ions was used for analysis. The Monte Carlo simulation code McChasy was applied for spectra evaluation. Fig. 1. Random and aligned RBS/channeling spectra for 1 μm thick GaN film bombarded to different fluences of 320 keV Ar ions. ~ 1000 nm ~ 40 nm GaN Al 2 O 3 bul k Fig. 2. Depth distributions of displaced lattice atoms due to Ar- ion bombardment DISCUSSION AND CONCLUSIONS Fig. 3 shows the defect buildup curves for studied alloys. The multistep damage accumulation model [1] has been fitted to the data. For comparison results of Ar-ion bombardment at 15 K [2] were also shown. At a given fluence phase transformations in bombarded epilayers occur, which are visualized as steps in calculated curves. Three step process has been assumed. Parameters of corresponding transitions are listed in Table 1. One notes that the critical fluence for the second step is independent of the Al molar quotient. Our preliminary HRXRD data indicate that the driving force for this effect is the strain accumulation in implanted layer. Besides of GaN the amorphization cannot be attained with 320 keV Ar-ion bombardment. Further increase of the ion fluence leads only to enhanced sputtering and cannot produce more damage. Fig. 3. Accumulated damage in GaN, AlGaN and AlN epilayers bombarded with 320 keV Ar ions. Solid lines are fits to RBS/C data using the MSDA model assuming a three-step process AIM The detailed understanding of defect formation and transformations in AlGaN is of great interest for further material and device improvement. Because of the complexity of processes involved in defect buildup, many important issues are still to be elucidated. Nucleatio n Layer depth (nm ) 0 100 200 300 400 displaced atom s (% ) 0 20 40 60 80 100 120 virgin 5E14 2E15 5E15 1E17 TRIM dpa 0,01 0,1 1 10 100 1000 accum ulated dam age (% ) 0 20 40 60 80 100 120 experim entGaN experim entG aN W endler experim entA l 0.4 Ga 0.6 N experimentAlN ACKNOWLEDGEMENTS This work was supported by the Polish Ministry of Science and Higher Education, Grant No. N 51502931/1104. RBS/channeling analysis has been carried out at the AIM of the Institute of Ion Beam Physics and Materials Research of the Forschungszentrum Dresden-Rossendorf within the framework of the specific research and technological development programme of the European Community "Structuring the European Research Area: Research Infrastructures Transnational Access” (RITA Contract Number 025646). Table 1. MSDA model parameters: RESULTS Fig. 1 shows random and (0001) aligned spectra (Ga peak only) for 1 μm thick GaN epilayers subjected to Ar-ion bombardment to different fluences. Some characteristic features of spectra should be pointed out: •with increasing Ar fluence Ga damage peak increases monotonically due to the progressing damage builup in GaN layer, •for the highest fluence the implanted region was amorphized, •peak in the vicinity of the rear edge is due to the lattice mismatch between the layer and the substrate and is characteristic for heteroepitaxial GaN growth. Similar spectra were obtained for Ar-ion implanted Al 0.4 Ga 0.6 N and AlN layers. REFERENCES [1] J. Jagielski et al. NIMB 266 (2008) 2902. [2] E. Wendler et al. NIMB 206 (2003) 1028. fdi- level of damage at saturation , σi-cross-section for damage formation (slope), xi- irradiation fluence in dpa, where i – stage number. GaN GaN Wendler Al 0.4 Ga 0.6 N AlN fd1 6 7.5 6 0.5 σ1 0.77 2.15 4.8 0.5 fd2 70 75 42 6.5 σ2 0.151 0.258 0.16 7.8 x2 3 2.1 0.7 0.06 fd3 100 100 54 63.5 σ3 0.02 0.079 0.022 0.168 x3 88 14 60 1.26
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Transcript of Compositional dependence of damage buildup in Ar-ion bombarded AlGaN K. Pągowska 1, R. Ratajczak 1,...
Compositional dependence of damage buildup in Ar-ion bombarded AlGaN
K. Pągowska1, R. Ratajczak1, A. Stonert 1, L. Nowicki1 and A. Turos 1,2
1 Soltan Institute for Nuclear Studies, 05-400 Świerk/Otwock, Poland 2 Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw, Poland
channel number100 200 300 400 500 600 700 800
yie
ld (
co
un
ts)
0
500
1000
1500
2000
2500
3000 random virgin 5E14 2E15 5E15 1E17
SAMPLE PREPARATION
GaN, Al0.4Ga0.6N and AlN layers of 1 μm thickness were grown on sapphire substrates
using the MOVPE technique.
Epitaxial layers were bombarded with 320 keV Ar ions to fluence ranging from 5х1012 to 1х1017/cm2 at RT.
EXPERIMENTAL
RBS/channeling with 1.70 MeV 4He-ions was used for analysis. The Monte Carlo simulation code McChasy was applied for spectra evaluation.
Fig. 1.Random and aligned RBS/channeling spectra for 1 μm thick GaN film bombarded to different fluences of 320 keV Ar ions.
~ 1000 nm~ 40 nm
GaNAl2O3
bulk
Fig. 2.Depth distributions of displaced lattice atoms due to Ar-ion bombardment
DISCUSSION AND CONCLUSIONS
Fig. 3 shows the defect buildup curves for studied alloys. The multistep damage accumulation model [1] has been fitted to the data. For comparison results of Ar-ion bombardment at 15 K [2] were also shown. At a given fluence phase transformations in bombarded epilayers occur, which are visualized as steps in calculated curves. Three step process has been assumed. Parameters of corresponding transitions are listed in Table 1. One notes that the critical fluence for the second step is independent of the Al molar quotient. Our preliminary HRXRD data indicate that the driving force for this effect is the strain accumulation in implanted layer. Besides of GaN the amorphization cannot be attained with 320 keV Ar-ion bombardment. Further increase of the ion fluence leads only to enhanced sputtering and cannot produce more damage.
Fig. 3. Accumulated damage in GaN, AlGaN and AlN epilayers bombarded with 320 keV Ar ions. Solid lines are fits to RBS/C data using the MSDA model assuming a three-step process
AIM The detailed understanding of defect formation and transformations in AlGaN is of great
interest for further material and device improvement. Because of the complexity of processes involved in defect buildup, many important issues are still to be elucidated.
Nucleatio
nLaye
r
depth (nm)0 100 200 300 400
dis
pla
ce
d a
tom
s (
%)
0
20
40
60
80
100
120
virgin 5E14 2E15 5E15 1E17 TRIM
dpa0,01 0,1 1 10 100 1000
accu
mu
late
d d
amag
e (%
)
0
20
40
60
80
100
120
experiment GaNexperiment GaN Wendlerexperiment Al0.4Ga0.6N
experiment AlN
ACKNOWLEDGEMENTSThis work was supported by the Polish Ministry of Science and Higher Education, Grant No. N 51502931/1104. RBS/channeling analysis has been carried out at the AIM of the Institute of Ion Beam Physics and Materials Research of the Forschungszentrum Dresden-Rossendorf within the framework of the specific research and technological development programme of the European Community "Structuring the European Research Area: Research Infrastructures Transnational Access” (RITA Contract Number 025646).
Table 1.
MSDA model parameters:
RESULTSFig. 1 shows random and (0001) aligned spectra (Ga peak only) for 1 μm thick GaN epilayers
subjected to Ar-ion bombardment to different fluences. Some characteristic features of spectra should be pointed out:
•with increasing Ar fluence Ga damage peak increases monotonically due to the progressing damage builup in GaN layer,
•for the highest fluence the implanted region was amorphized,•peak in the vicinity of the rear edge is due to the lattice mismatch between the layer and the
substrate and is characteristic for heteroepitaxial GaN growth.Similar spectra were obtained for Ar-ion implanted Al0.4Ga0.6N and AlN layers.
REFERENCES
[1] J. Jagielski et al. NIMB 266 (2008) 2902.[2] E. Wendler et al. NIMB 206 (2003) 1028.
fdi- level of damage at saturation ,σi-cross-section for damage formation (slope),xi- irradiation fluence in dpa,
where i – stage number.
GaNGaN
WendlerAl0.4Ga0.6N AlN
fd1 6 7.5 6 0.5
σ1 0.77 2.15 4.8 0.5
fd2 70 75 42 6.5
σ2 0.151 0.258 0.16 7.8
x2 3 2.1 0.7 0.06
fd3 100 100 54 63.5
σ3 0.02 0.079 0.022 0.168
x3 88 14 60 1.26
