Hyun-gi Hong

Highly efficient InGaN/GaN blue LED on 8-inch Si (111) substrate

We have grown LED structures on top of a robust n-type GaN template on 8-inch diameter silicon substrates achieving both a low dislocation density and a 7 um-thick template without crack even at a sufficient Si doping condition. Such high crystalline quality of n-GaN templates on Si were obtained by optimizing combination of stress compensation layers and dislocation reduction layers. Wafer bowing of LED structures were well controlled and measured below 20 μm and the warpage of LED on Si substrate was found to strongly depend on initial bowing of 8-inch Si substrates. The full-width at half-maximum (FWHM) values of GaN (0002) and (10-12) ω-rocking curves of LED samples grown on 8-inch Si substrates were 220 and 320 arcsec. The difference between minimum and maximum of FWHM GaN (0002) was 40 arcsec. The dislocation densities were measured about 2~3×108/cm2 by atomic force microscopy (AFM) after in-situ SiH4 and NH3 treatment. The measured quasi internal quantum efficiency of 8-inch InGaN/GaN LED was ~ 90 % with excitation power and temperature-dependent photoluminescence method. Under the un-encapsulated measurement condition of vertical InGaN/GaN LED grown on 8-inch Si substrate, the overall output power of the 1.4×1.4 mm2 chips representing a median performance exceeded 484 mW with the forward voltage of 3.2 V at the driving current of 350 mA.

Highly efficient InGaN/GaN blue LEDs on large diameter Si (111) substrates comparable to those on sapphire

Highly efficient InGaN/GaN LEDs grown on 4- and 8-inch silicon substrates comparable to those on sapphire substrates have been successfully demonstrated. High crystalline quality of n-GaN templates on Si were obtained by optimizing combination of stress compensation layers and dislocation reduction layers. The full-width at half-maximum (FWHM) values of GaN (0002) and (10-12) ω-rocking curves of n-GaN templates on 4-inch Si substrates were 205 and 290 arcsec and those on 8-inch Si substrate were 220 and 320 arcsec, respectively. The dislocation densities were measured about 2~3×108/cm2 by atomic force microscopy (AFM) after in-situ SiH4 and NH3 treatment. Under the unencapsulated measurement condition of vertical InGaN/GaN LED grown on 4-inch Si substrate, the overall output power of the 1.4×1.4 mm2 chips representing a median performance exceeded 504 mW with the forward voltage of 3.2 V at the driving current of 350 mA. These are the best values among the reported values of blue LEDs grown on Si substrates. The measured internal quantum efficiency was 90 % at injection current of 350 mA. The efficiency droops of vertical LED chips on Si between the maximum efficiency and the efficiency measured at 1A (56.69 A/cm2) input current was 5%.

Highly efficient InGaN/GaN blue LED grown on Si (111) substrate

For the first time, based on the high crystalline quality of n-GaN on Si template, highly efficient InGaN/GaN LEDs grown on 4-inch silicon substrates comparable to those on sapphire substrates have been successfully demonstrated. At driving current of 350 mA, the overall output power of 1×1 mm2 LED chips exceeded 420 mW and forward voltage was 3.2 V under un-encapsulated condition, which is the best value among the reported values of blue LED grown on Si substrates. The internal quantum efficiency of 76% at injection current of 350 mA was measured.

Fabrication and characterization of the Si-photonics-integrated vertical resonant-cavity light-emitting diode

We designed and fabricated a 1.3-um hybrid vertical Resonant-Cavity Light-Emitting Diode for optical interconnect by using direct III-V wafer bonding on silicon on insulator (SOI). The device included InP based front distributed Bragg reflector (DBR), InGaAlAs based active layer, and SOI-based high-contrast-grating (HCG) as a back reflector. 42-uW continuous wave optical power was achieved at 20mA at room temperature.