Nitrides Seminar - Abdullah Almogbel, Graduate Student Researcher
2/6/2020 12PM ESB 1001
Abdullah Almogbel, PhD candidate
Speck group, UCSB Materials Department
Efficient deep ultraviolet light emitting diodes grown on silicon carbide substrates
Deep UV LEDs with wavelength
< 280 nm are projected in the near future to penetrate into several key industrial and medical applications such as water purification and surface sterilization as well as gas sensing and secure communications. So far, Aluminum gallium nitride (AlGaN) alloy is the only material that can be employed to develop UV LEDs. AlGaN has tunable wavelength emission that spans the UV range from 210 nm to 360 nm and has been used to develop commercial UV LEDs. Recently, deep UV laser has been also demonstrated using AlGaN. However, commercial deep UV LEDs are still lagging far behind visible LEDs in terms of output power, lifetime and cost. Some of the UV LEDs inefficiencies can be attributed directly to the AlGaN intrinsic properties. AlGaN has nonideal wurtzite structure, the nonideality and bonding ionicity increases as the aluminum composition increase which expected to cause anisotropic light emission and higher activation energy of dopants, both of which are major inefficiency factors. Therefore, novel techniques are essential to overcome these fundamental challenges. Due to the lack of native substrate, our approach to develop high efficiency UV LED in the range (260 nm <
< 280 nm) relies on growing AlGaN on silicon carbide (SiC) substrates using metalorganics chemical vapor deposition. In this talk, AlGaN intrinsic properties that influence the UV LED efficiency will be reviewed as well as the advantage of our approach to grow on SiC instead of sapphire. The main focus will be on the n-type doping of AlGaN and active region design, explaining the growth and characterization methods that were used for optimizing the structural and electrical qualities of AlGaN.
B. K. SaifAddin, A. Almogbel, C. J. Zollner, H. Foronda, A. Alyamani, A. Albadri, M. Iza, S. Nakamura, S. P. DenBaars, and J. S. Speck, “Fabrication technology for high light-extraction ultraviolet thin-film flip-chip (UV TFFC) LEDs grown on SiC,” Semicond. Sci. Technol., vol. 34, no. 3, p. 035007, Mar. 2019.
C. J. Zollner, A. Almogbel, Y. Yao, B. K. SaifAddin, F. Wu, M. Iza, S. P. DenBaars, J. S. Speck, and S. Nakamura, “Reduced dislocation density and residual tension in AlN grown on SiC by metalorganic chemical vapor deposition,” Appl. Phys. Lett., vol. 115, no. 16, p. 161101, Oct. 2019.