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<1-210> zone axis (0002) (10-10) GaN nanorods grown on Si (111) substrate by Plasma-Assisted Molecular Beam Epitaxy IV.Conclus ions ademia Sinica search Center for Applied Sciences I. Abstract S.T. Chou 1 , S.H. Tsai 1 , M.Y. Lin 1 , W.H. Liao 1 , Shih-Yen Lin *, 1, 2 , 1 Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei, Taiwan 2 Department of Photonics, National Chiao-Tung University, Hsinchu, Taiwan *Tel. ： +886-3-5744364, Fax ： +886-3-5745233, e-mail ： [email protected] 3. TEM images and SAD patterns 4. The Micro-PL spectra II. Experiments The vertically c-axis aligned GaN nanorod arrays grown by plasma-assisted molecular-beam epitaxy are epitaxially oriented on Si(111) substrates without buffer layer and their crystal structure corresponds to a fully relaxed wurtzite lattice. At later growth stage, these GaN nanorods exhibit the tendency to coalesce into nanorod bundles. The GaN nanorods are demonstrated and analyzed with FE-SEM, TEM, Micro-PL, and Micro-Raman techniques. GaN nanorods structures posses the advantages of strain-free and dislocation-free. Thus GaN nanorods are very promising material for device fabrication of high efficiency LEDs. 2. FE-SEM images m-plane [1 0 -1 0] a- plane [1 1 - 2 0] Sample A 550 600 650 700 750 5.0x10 2 1.0x10 3 1.5x10 3 2.0x10 3 2.5x10 3 3.0x10 3 Sam ple A Sam ple B Sam ple C Sam ple D 566.96 cm -1 566.96 cm -1 566.96 cm -1 566.96 cm -1 @ 300 K H e-N e L aser (633 nm ) D etector : Si P inhole = 200 m G rating = 1200 lines/m m E xposure tim e = 30 sec R am an sh ift In ten sity (a.u .) W avenum b er (cm -1 ) II. Results and discussion Sample A Sample B Sample C Sample D Sample B Sample B (T S =790 ℃) Si (111) substrate 1300 nm n-GaN Sample C (T S =790 ℃) 500 nm n-GaN Sample D (T S =790 ℃) 200 nm i-GaN 500 nm n-GaN 500 nm n-GaN 1 nm i-GaN 500 nm n-GaN 1 nm AlN 1 nm AlN Sample A (T S =780 ℃) 200 nm i-GaN Growth direction Sample B Sample A Sample C Sample C Sample D Sample D Sample B 5. The Micro-Raman spectra (000-2) (0000) (-1010) Fig. 2 Cross-sectional and plan view FE-SEM images of the GaN nanostructures grown on Si (111) substrate without buffer layer. 1. RHEED pattern Fig. 1 GaN nanorod RHEED patterns of different plane, which correspond to the GaN surface morphologies. Fig. 3 TEM image of a single free-standing GaN nanorod (a) The nanorod is nearly dislocation free. (b) A selected-area diffraction of the nanorod exhibits a wurtzite structure with elecctron beam along <1-210> zone-axis. (a) (b) Fig. 4 Room-temperature micro-PL spectrum for GaN nanorods. Table. 1 The GaN nanorod structure and growth conditions of sampleA to D that grown on Si (111) substrates without buffer layer. Fig. 5 Room-temperature micro-Raman spectra for GaN nanorods.GaN E 2 (high) mode at 567 cm -1 also support that GaN nanorods are strain-free. In summary, we have confirmed that PAMBE-grown wurtzite GaN nanorods are completely relaxed, strain-free single crystals and they are epitaxially oriented on the Si (111) substrate. Both V/III ratio and substrate temperature play very important roles in the nanorods growth.
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GaN nanorods grown on Si (111) substrate by Plasma-Assisted Molecular Beam Epitaxy. I. Abstract. II. Experiments. III. Results and discussion. Sample A (T S =780 ℃ ). Sample B (T S =790 ℃). Sample C (T S =790 ℃). Sample D (T S =790 ℃). 500 nm n-GaN. 500 nm n-GaN. Growth direction. - PowerPoint PPT Presentation
Transcript of zone axis
<1-210> zone axis
(0002)(10-10)
GaN nanorods grown on Si (111) substrateby Plasma-Assisted Molecular Beam Epitaxy
IV.Conclusions
Academia SinicaResearch Center for Applied Sciences
I. Abstract
S.T. Chou1, S.H. Tsai1, M.Y. Lin1, W.H. Liao1, Shih-Yen Lin*, 1, 2, 1Research Center for Applied Sciences, Academia Sinica, Nankang, Taipei, Taiwan
2Department of Photonics, National Chiao-Tung University, Hsinchu, Taiwan*Tel. ： +886-3-5744364, Fax ： +886-3-5745233, e-mail ： [email protected]
3. TEM images and SAD patterns
4. The Micro-PL spectra
II. Experiments
The vertically c-axis aligned GaN nanorod arrays grown by plasma-assisted molecular-beam epitaxy are epitaxially oriented on Si(111) substrates without buffer layer and their crystal structure corresponds to a fully relaxed wurtzite lattice. At later growth stage, these GaN nanorods exhibit the tendency to coalesce into nanorod bundles. The GaN nanorods are demonstrated and analyzed with FE-SEM, TEM, Micro-PL, and Micro-Raman techniques. GaN nanorods structures posses the advantages of strain-free and dislocation-free. Thus GaN nanorods are very promising material for device fabrication of high efficiency LEDs.
2. FE-SEM images
m-plane[1 0 -1 0]
a-plane[1 1 -2 0]Sample A
550 600 650 700 750
5.0x102
1.0x103
1.5x103
2.0x103
2.5x103
3.0x103
Sample A Sample B Sample C Sample D
566.96 cm-1
566.96 cm-1
566.96 cm-1
566.96 cm-1
@ 300 KHe-Ne Laser (633 nm)Detector : SiPinhole = 200 mGrating = 1200 lines/mmExposure time = 30 sec
Ram
an s
hif
t In
ten
sity
(a.
u.)
Wavenumber (cm-1)
III. Results and discussion
Sample A Sample B Sample C Sample D
Sample B
Sample B(TS=790 )℃
Si (111) substrate
1300 nm n-GaN
Sample C(TS=790 )℃
500 nm n-GaN
Sample D(TS=790 )℃
200 nm i-GaN
500 nm n-GaN 500 nm n-GaN
1 nm i-GaN
500 nm n-GaN
1 nm AlN
1 nm AlN
Sample A(TS=780 ℃)
200 nm i-GaN
Grow
th
direction
Sample B
Sample A
Sample C Sample C
Sample D Sample D
Sample B
5. The Micro-Raman spectra
(000-2)(0000)
(-1010)
Fig. 2 Cross-sectional and plan view FE-SEM images of the GaN nanostructures grown on Si (111) substrate without buffer layer.
1. RHEED pattern
Fig. 1 GaN nanorod RHEED patterns of different plane, which correspond to the GaN surface morphologies.
Fig. 3 TEM image of a single free-standing GaN nanorod (a) The nanorod is nearly dislocation free. (b) A selected-area diffraction of the nanorod exhibits a wurtzite structure with elecctron beam along <1-210> zone-axis.
(a) (b)
Fig. 4 Room-temperature micro-PL spectrum for GaN nanorods.
Table. 1 The GaN nanorod structure and growth conditions of sampleA to D that grown on Si (111) substrates without buffer layer.
Fig. 5 Room-temperature micro-Raman spectra for GaN nanorods.GaN E2(high) mode at 567 cm-1 also support that GaN nanorods are strain-free.
In summary, we have confirmed that PAMBE-grown wurtzite GaN nanorods are completely relaxed, strain-free single crystals and they are epitaxially oriented on the Si (111) substrate. Both V/III ratio and substrate temperature play very important roles in the nanorods growth.
