Name: graphene-assisted quasi-van der waals epitaxy of aln film on nano-patterned sapphire substrate for ultraviolet light emitting diodes
Uploaded: 2020-06-25T12:30:00
Description: Watch this Scientific Journal Video about Graphene-Assisted Quasi-van der Waals Epitaxy of AlN Film on Nano-Patterned Sapphire Substrate for Ultraviolet Light Emitting Diodes at JoVE.com

This work was financially supported by the National Key R&#38;D Program of China (No. 2018YFB0406703), the National Natural Science Foundation of China (Nos. 61474109, 61527814, 11474274, 61427901), and the Beijing Natural Science Foundation (No. 4182063)

CAUTION: Several of the chemicals used in these methods are acutely toxic and carcinogenic. Please consult all relevant material safety data sheets (MSDS) before use.
1. Preparation of NPSS by nanoimprint lithography (NIL)
<ol>
	<li>Deposition of SiO2 film
	<ol>
		<li>Wash the 2&#34;&#160;c-plane flat sapphire substrate with ethanol followed by deionized water three times.</li>
		<li>Dry the substrate with a nitrogen gun.</li>
		<li>Deposit 200 nm SiO2 film on the flat ...

<ol>
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Technology. 26, 014036 (2010).</li><li>Kunook, C., Chul-Ho, L., Gyu-Chul, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transferable+GaN+layers+grown+on+ZnO-coated+graphene+layers+for+optoelectronic+devices.">Transferable GaN layers grown on ZnO-coated graphene layers for optoelectronic devices.</a> Science. 330, 655-657 (2010).</li><li>Kim, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Principle+of+direct+van+der+Waals+epitaxy+of+single-crystalline+films+on+epitaxial+graphene.">Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene.</a> Nature Communications. 5, 4836 (2014).</li><li>Han, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+heat+dissipation+in+gallium+nitride+light-emitting+diodes+with+embedded+graphene+oxide+pattern.">Improved heat dissipation in gallium nitride light-emitting diodes with embedded graphene oxide pattern.</a> Nature Communications. 4, 1452 (2013).</li><li>Gupta, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MOVPE+growth+of+semipolar+III-nitride+semiconductors+on+CVD+graphene.">MOVPE growth of semipolar III-nitride semiconductors on CVD graphene.</a> Journal of Crystal Growth. 372, 105-108 (2013).</li><li>Heinke, H., Kirchner, V., Einfeldt, S., Hommel, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=X-ray+diffraction+analysis+of+the+defect+structure+in+epitaxial+GaN.">X-ray diffraction analysis of the defect structure in epitaxial GaN.</a> Appllied Physics Letters. 77, 2145-2147 (2000).</li><li>Lughi, V., Clarke, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defect+and+Stress+Characterization+of+AlN+Films+by+Raman+Spectroscopy.">Defect and Stress Characterization of AlN Films by Raman Spectroscopy.</a> Appllied Physics Letters. 89, 2653 (2006).</li><li>Li, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Van+der+Waals+epitaxy+of+GaN-based+light-emitting+diodes+on+wet-transferred+multilayer+graphene+film.">Van der Waals epitaxy of GaN-based light-emitting diodes on wet-transferred multilayer graphene film.</a> Jappanese Journal of Applied Physics. 56, 085506 (2017).</li><li>Chang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene-assisted+quasi-van+der+Waals+epitaxy+of+AlN+film+for+ultraviolet+light+emitting+diodes+on+nano-patterned+sapphire+substrate.">Graphene-assisted quasi-van der Waals epitaxy of AlN film for ultraviolet light emitting diodes on nano-patterned sapphire substrate.</a> Applled Physics Letters. 114, 091107 (2019).</li></ol>

As shown in Figure 1A, the NPSS prepared by the NIL technique illustrates the nano-concave cone patterns with 400 nm depth, 1 &#956;m period of pattern, and 300 nm width of the unetched regions. After the APCVD growth of graphene layer, the graphene-NPSS is shown in Figure 1B. The significant increased D peak of N-plasma treated graphene in Raman spectra Figure 1C demonstrates the i...

AlN and AlGaN are the most essential materials in DUV-LEDs1,2, which have been widely used in various fields such as sterilization, polymer curing, biochemical detection, non-line-of-sight communication, and special lighting3. Due to the lack of intrinsic substrates, AlN heteroepitaxy on sapphire substrates by MOCVD has become the most common technical route4. However, the large lattice mismatch between AlN and sapphire substrate leads to stress accumulation5,6, high density dislocations, and stacking faults7. Thus, the internal quantum efficiency of LEDs are reduced8. In recent decades, using patterned sapphire as substrates (PSS) to induce AlN epitaxial lateral overgrowth (ELO) has been proposed to solve this problem. In addition, great progress has been made in the growth of AlN templates9,10,11. However, with a high surface adhesion coefficient and bonding energy (2.88 eV for AlN), Al atoms have low atomic surface mobility, and the growth of AlN tends to have a three-dimensional island growth mode12. Thus, the epitaxial growth of AlN films on NPSS is difficult and requires higher coalescence thickness (over 3 &#956;m) than that on flat sapphire substrates, which causes longer growth time and requires high costs9.
Recently, graphene shows great potential for use as a buffer layer for AlN growth due to its hexagonal arrangement of sp2 hybridized carbon atoms13. In addition, the quasi-van der Waals epitaxy (QvdWE) of AlN on graphene may reduce the mismatch effect and has paved a new way for AlN growth14,15. To increase the chemical reactivity of graphene, Chen et al. used N2-plasma treated graphene as a buffer layer and determined the QvdWE of high quality AlN and GaN films8, which demonstrates the utilization of graphene as a buffer layer.
Combining the N2-plasma treated graphene technic with commercial NPSS substrates, this protocol presents a new method for quick growth and coalescence of AlN on a graphene-NPSS substrate. The completely coalesce thickness of AlN on graphene-NPSS is confirmed to be less than 1 &#181;m, and the epitaxial AlN layers are of high quality and stress-released. This method paves a new way for AlN template mass production and shows great potential in the application of AlGaN-based DUV-LEDs.

<table>
	<tbody>
		<tr>
			<td>Acetone,99.5%</td>
			<td>Bei Jing Tong Guang Fine Chemicals company</td>
			<td>1090</td>
			<td></td>
		</tr>
		<tr>
			<td>APCVD</td>
			<td>Linderberg</td>
			<td>Blue M</td>
			<td></td>
		</tr>
		<tr>
			<td>EB</td>
			<td>AST</td>
			<td>Peva-600E</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethonal,99.7%</td>
			<td>Bei Jing Tong Guang Fine Chemicals company</td>
			<td>1170</td>
			<td></td>
		</tr>
		<tr>
			<td>HF,40%</td>
			<td>Beijing Chemical Works</td>
			<td>1789</td>
			<td></td>
		</tr>
		<tr>
			<td>ICP-RIE</td>
			<td>AST</td>
			<td>Cirie-200</td>
			<td></td>
		</tr>
		<tr>
			<td>MOCVD</td>
			<td>VEECO</td>
			<td>P125</td>
			<td></td>
		</tr>
		<tr>
			<td>PECVD</td>
			<td>Oerlikon</td>
			<td>790+</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate,85%</td>
			<td>Beijing Chemical Works</td>
			<td>1805</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfuric acid,98%</td>
			<td>Beijing Chemical Works</td>
			<td>10343</td>
			<td></td>
		</tr>
	</tbody>
</table>

graphene-assisted quasi-van der waals epitaxy of aln film on nano-patterned sapphire substrate for ultraviolet light emitting diodes

This protocol demonstrates a method for graphene-assisted quick growth and coalescence of AlN on nano-pattened sapphire substrate (NPSS). Graphene layers are directly grown on NPSS using catalyst-free atmospheric-pressure chemical vapor deposition (APCVD). By applying nitrogen reactive ion etching (RIE) plasma treatment, defects are introduced into the graphene film to enhance chemical reactivity. During metal-organic chemical vapor deposition (MOCVD) growth of AlN, this N-plasma treated graphene buffer enables AlN quick growth, and coalescence on NPSS is confirmed by cross-sectional scanning electron microscopy (SEM). The high quality of AlN on graphene-NPSS is then evaluated by X-ray rocking curves (XRCs) with narrow (0002) and (10-12) full width at half-maximum (FWHM) as 267.2 arcsec and 503.4 arcsec, respectively. Compared to bare NPSS, AlN growth on graphene-NPSS shows significant reduction of residual stress from 0.87 GPa to 0.25 Gpa, based on Raman measurements. Followed by AlGaN multiple quantum wells (MQWS) growth on graphene-NPSS, AlGaN-based deep ultraviolet light-emitting-diodes (DUV LEDs) are fabricated. The fabricated DUV-LEDs also demonstrate obvious, enhanced luminescence performance. This work provides a new solution for the growth of high quality AlN and fabrication of high performance DUV-LEDs using a shorter process and less costs.

Scanning electron microscopy (SEM) images, X-ray diffraction rocking curves (XRC), Raman spectra, transmission electron microscopy (TEM) images, and electroluminescence (EL) spectrum were collected for the epitaxial AlN film (Figure 1, Figure 2) and AlGaN-based DUV-LEDs (Figure 3). The SEM and TEM are used to determine the morphology of the AlN on graphene-NPSS. XRD and Raman are used to calculate the dislocation densities and the r...

Watch this Scientific Journal Video about Graphene-Assisted Quasi-van der Waals Epitaxy of AlN Film on Nano-Patterned Sapphire Substrate for Ultraviolet Light Emitting Diodes at JoVE.com

Graphene-Assisted Quasi-van der Waals Epitaxy of AlN Film on Nano-Patterned Sapphire Substrate for Ultraviolet Light Emitting Diodes

A protocol for graphene-assisted growth of high-quality AlN films on nano-patterned sapphire substrate is presented.

This protocol demonstrates a method for graphene-assisted quick growth and coalescence of AlN on nano-pattened sapphire substrate (NPSS). Graphene layers ...

This new protocol for aluminum nitrides quick growth on nano-patterned sapphire substrate with graphene layer can be used for rapid and inexpensive generation of high-performing deep ultraviolet LEDs. Using di-eel graphene as the aluminum nitride template, shows growth potential in the application of aluminum, gallium nitrite based LEDs. To begin, rinse the NPSS with acetone, ethanol and deionized water three times.And dry the NPSS with a nitrogen gun. Load the NPSS into a three-zone, high temperature furnace, with a long flat temperature zone. And heat the furnace to 1050 degrees Celsius.Stabilize the temperature for 10 minutes under 500 standard cubic centimeters per minute of argon and 300 standard cubic centimeters per minute of argon of hydrogen. Then introduce 30 standard cubic centimeters per minute of argon of methane into the reaction chamber for the growth of the graphene on the NPSS for three hours. At the end of the growth reaction, switch off the methane and allow the NPSS to cool naturally.Rinse the cooled substrate with deionized water. And dry the NPSS with a nitrogen gun. Then, etch the graphene NPSS by nitrogen plasma with a nitrogen flow rate of 300 standard cubic centimeters per minute for 30 seconds.And a power of 50 watts in reactive ion etching chamber. For MOCVD growth of aluminum nitrogen on graphene NPSS, edit the MOCVD recipe for aluminum nitrogen growth. And load the graphene NPSS and its NPSS counterpart into a homemade MOCVD chamber.After heating for 12 minutes, the temperature will stabilize at 1200 degrees Celsius. Then introduce 7000 standard cubic centimeters per minute of hydrogen as ambient. 70 standard cubic centimeters per minute trimethylaluminum.And 500 standard cubic centimeters per minute ammonia for two hours. Proceed with MOCVD growth of aluminum gallium nitrogen quantum wells according to manuscript directions. When finished, lower the temperature of the chamber to 800 degrees Celsius and a-kneel the P-type layers with nitrogen for 20 minutes.For aluminum gallium nitrogen based deep ultraviolet LED fabrication, spin photo-resist 4620 onto the wafers and perform lithography with eight seconds of UV exposure, 30 seconds of developing time and two minutes of rinsing time. For inductive coupled plasma etching of P-gallium nitrogen, set the etching power to 450 watts, the etching pressure to four millitorrs and the etching rate to 5.6 nanometers per second. Place the etched sample into acetone at 80 degrees Celsius for five minutes.Followed by washing in ethanol and deionized water. Spinning negative photo-resist the NR9 and the lithography for a UV exposure time of 12 seconds, a developing time of 20 seconds and a rinsing time of two minutes. Wash the sample with acetone, ethanol and deionized water three times.And deposit titanium aluminum titanium gold by electron beam evaporation. Spin negative photo-resist NR9 and lithography under the same settings. And wash the samples three times with acetone, ethanol and deionized water without ultrasonication.Deposit nickel-gold by electron beam evaporation. And wash the sample with ethanol and deionized water three times. Deposit 300 nanometers of silicon dioxide by plasma-enhanced chemical vapor deposition at a deposition temperature of 300 degrees Celsius and a deposition rate of 100 nanometers per minute.Spin photo-resist 304 and lithography at a UV exposure time of eight seconds, a developing time of one minute and a rinsing time of two minutes before immersing the wafers into 23%hydrofluoric acid for 15 seconds. Wash the sample three times with ethanol and deionized water. And dry the wafers with a nitrogen gun.After photo lithography with NR9 as demonstrated, deposit aluminum titanium gold by electron beam evaporation. And wash the sample three times with ethanol and deionized water. After the last wash grind and polish the sapphire to 130 micrometers by mechanical polishing.And wash the sample with de-waxing solution and deionized water. Then use a laser to cut the whole wafer into 0.5 by 0.5 millimeter device pieces. And use a mechanical dicer to cut the wafer into chips.Scanning and transmission electron microscopy imaging can be used to determine the morphology of the aluminum nitrogen on graphene and NPSS. Ramen can be used to calculate the dislocation densities and the residual stress. Electroluminescense is used to illustrate the illumination of the fabricated deep UV LEDs.Remember that the wafer must be clean before each new modification. So it is essential to rinse the wafer thoroughly before every step.

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