Tak Jeong

Publications (3)6.11 Total impact

• Article: Aluminum Nitride Ceramic Substrates-Bonded Vertical Light-Emitting Diodes

  Tak Jeong, Kang Ho Kim, Seung Jae Lee, Sang Hern Lee, Seong Ran Jeon, Sue Hyun Lim, Jong Hyeob Baek, J.K. Lee
  [show abstract] [hide abstract]
  ABSTRACT: We confirmed the potential of an aluminum nitride (AlN) substrate to be used as a bonding material for the high current operation of vertical light-emitting diodes (VLEDs). For the electrical connection to the top and bottom of the AlN substrate, via-holes were formed by laser drilling and then filled with Ag, which plays a role in improving the thermal dissipation from the VLEDs. The forward voltage of the fabricated AlN-bonded VLEDs was 3.54 V at 350 mA, which is similar to that of the Si-bonded VLEDs. It was also found that the light output power of the AlN-bonded VLEDs increased steadily with increasing injection current up to 1 A, while that of the Si-bonded VLEDs started to decrease at around 850 mA. In addition, the thermal resistance of the AlN-bonded VLEDs was significantly reduced, as compared with that of the Si-bonded VLEDs and conventional LEDs, under the same package conditions.
  IEEE Photonics Technology Letters 08/2009; · 2.19 Impact Factor
• Article: Enhanced Light Output Power of GaN-Based Vertical Light-Emitting Diodes by Using Highly Reflective ITO–Ag–Pt Reflectors

  Tak Jeong, Kang Ho Kim, Hyun Haeng Lee, Seung Jae Lee, Sang Hern Lee, Jong Hyeob Baek, June Key Lee
  [show abstract] [hide abstract]
  ABSTRACT: Highly reflective and thermally stable indium-tin-oxide (ITO)-Ag-Pt p-type reflectors for use in high-performance GaN-based light-emitting diodes (LEDs) have been investigated. The specific contact resistance of the ITO-Ag-Pt contacts was found to be 7.2 ×10^-5Omegamiddotcm². The ITO-Ag-Pt contacts showed a higher reflectance after thermal annealing (82% at 460 nm), while the reflectance of the ITO-Ag contacts was reduced from 81% to 65%. In addition, surface agglomeration was drastically decreased, indicating that the Pt layer efficiently prevents the surface agglomeration of the Ag layer. The vertical LEDs (VLEDs) fabricated with the ITO-Ag-Pt contacts had a 17% higher output power (at 20 mA) than the VLEDs fabricated with the ITO-Ag contacts.
  IEEE Photonics Technology Letters 01/2009; · 2.19 Impact Factor
• Article: Chemical lift-off of (11–22) semipolar GaN using periodic triangular cavities

  Dae-Woo Jeon, Seung-Jae Lee, Tak Jeong, Jong Hyeob Baek, Jae-Woo Park, Lee-Woon Jang, Myoung Kim, In-Hwan Lee, Jin-Woo Ju
  [show abstract] [hide abstract]
  ABSTRACT: Chemical lift-off of (11–22) semipolar GaN using triangular cavities was investigated. The (11–22) semipolar GaN was grown using epitaxial lateral overgrowth by metal-organic chemical vapor deposition on m-plane sapphire, in such a way as to keep N terminated surface of c-plane GaN exposed in the cavities. After regrowing 300 μm thick (11–22) semipolar GaN by hydride vapor phase epitaxy for a free-standing (11–22) semipolar GaN substrate, the triangular cavities of the templates were chemically etched in molten KOH. The (000-2) plane in the triangular cavities can be etched in the [0002] direction with the high lateral etching rate of 196 μm/min. The resulting free-standing (11–22) semipolar GaN substrate was confirmed to be strain-free by the Raman analysis.Highlights► (11–22) semipolar GaN including periodic triangular cavities was grown by MOCVD. ► 300 μm thick (11–22) semipolar GaN was regrown to keep the exposed N-polar GaN. ► The N-polar GaN can be etched to (0002) direction with high etching rate. ► The thick (11–22) semipolar GaN was completely separated from the m-plane sapphire. ► The free-standing (11–22) semipolar GaN without m-sapphire was strain-free.
  Journal of Crystal Growth 338(1):134-138. · 1.73 Impact Factor