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

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.