Highly efficient deep-uv light-emitting diodes using AlN-based, deep-uv transparent glass electrodes

Transcription

1 Supporting Information Highly efficient deep-uv light-emitting diodes using AlN-based, deep-uv transparent glass electrodes Tae Ho Lee, Byeong Ryong Lee, Kyung Rock Son, Hee Woong Shin,, and Tae Geun Kim *, School of Electrical Engineering, Korea University, Seoul , Republic of Korea LED R&D Center, LED Division, LG Innotek Co., Ltd., Paju, , Republic of Korea Phone: ; Fax: S-1

2 Figure S1 Details on the fabrication of lateral-type DUV LEDs with AlN GEs using PEBD process. S-2

3 Figure S2. Retention measurement of the LRS current at 2 V for the AlN glass electrode after the PEBD for long-term stability. The extrapolated result relative to the delay indicates that the LRS of the AlN GE could be maintained for > 10 6 s. It has been predicted that the LRS should be maintainable for up to ten years, that is, the aging behavior of the conductivity should be stable, indicating that the CFs (current path) generated by the PEBD process are highly reliable for device application as a TCE. Figure S3. Ohmic behavior on a p-al 0.4 Ga 0.6 N contact layer. Typical I V characteristics measured for different TLM pattern spacings (5, 10, 15, 20, and 25 µm) of Ni/Au (50/150 nm) metal contacts and 10-nm ITO layers deposited on p-al 0.4 Ga 0.6 N contact layer. S-3

4 Figure S4. Ohmic behaviors of GE and Ni/Au on p-al 0.4 Ga 0.6 N AlGaN contact layers Typical plots for total resistance versus pad spacing of a) AlN GE after PEBD process and b) Ni/Au (50/150 nm) metal contact deposited on p-al 0.4 Ga 0.6 N. Figure S5. Measurement set-up for C-AFM. Schematic illustrations of C-AFM measurements in AlN GE before and after PEBD process. Currents were measured through the Si probe using a variable gain enhanced current amplifier with the current compliance set to be 10 na. Figure S6. XRD analysis before and after PEBD process. XRD spectra measured at p- Al 0.4 Ga 0.6 N. S-4

5 Figure S7. UPS spectra of 15-nm AlN GE and 10-nm ITO. (left) Measured UPS spectra of (red line) AlN GE and (green line) annealed 10-nm ITO. (right) Magnified UPS spectra in the secondary electron cutoff region of the left figure. Figure S8. Packaging information a) Schematic illustration of packaged sample using Al reflector cup. b) Actual sample after packaging c) Measured transmittance spectrum for polydimethylsiloxane (PDMS) encapsulant. S-5

6 Figure S9. Electroluminescence spectrum of AlGaN-based lateral-type DUV LEDs. Electroluminescence spectrum versus wavelength measured for 280-nm AlGaN LEDs with AlN GEs after PEBD process (50 samples). The rainbow color scale on the right-hand side is provided to evaluate the sample distributions. EQE / / 1240 % output power, current, photon wavelength (peak wavelength) 1 Figure S10. Equation used for calculating the EQE of DUV LEDs. The EQE was measured from the LED photo-electricity detecting system with a software that can calculate the EQE using the above equation. Figure S11. Dependence of the AlN layer thickness on the electrical and optical properties of DUV LEDs. Chip-to-chip uniformity statistical data in a) forward voltages and S-6

7 b) normalized EL intensities measured for 50 different 280-nm DUV LEDs with 15, 30, and 45-nm AlN GEs after the PEBD process. S-7

8 Figure S12. 3D FDTD simulation for AlGaN-based lateral-type DUV LEDs with AlN GEs and 10-nm ITO. a, b) FDTD computational structures of LEDs with (a) AlN GEs and (b) 10-nm ITO. c) Comparison of simulated optical transmittance as function of propagation distance of 15-nm AlN and 10-nm ITO single layers at 280 nm, respectively. d, e) Simulated contour plots of far-field radiations for LEDs with d) AlN GEs and e) 10-nm ITO. Normalized linear color scale for intensity distribution combined with F φ,θ 2 appears to right of plots. S-8

9 Supporting Information Movies: Movie S1: 5-speed (5x) PEBD process of 55 metal dots (Cr/Ni) using auto-probing contact system. AMI_movie S1.avi S-9

10 References (1) Yu, S.-F.; Lin, R.-M.; Chang, S.-J.; Chu, F.-C. Efficiency Droop Characteristics in InGaN- Based Near Ultraviolet-to-Blue Light-Emitting Diodes. Appl. Phys. Express 2012, 5, S-10