Near milliwatt power AlGaN-based ultraviolet light emitting diodes based on lateral epitaxial overgrowth of AlN on Si(111)

Abstract

We report on the growth, fabrication, and device characterization of AlGaN-based thin-film ultraviolet (UV) (k $ 359 nm) light emitting diodes (LEDs). First, AlN/Si(111) template is patterned. Then, a fully coalesced 7-lm-thick lateral epitaxial overgrowth (LEO) of AlN layer is realized on patterned AlN/Si(111) template followed by UV LED epi-regrowth. Metalorganic chemical vapor deposition is employed to optimize LEO AlN and UV LED epitaxy. Back-emission UV LEDs are fabricated and flip-chip bonded to AlN heat sinks followed by Si(111) substrate removal. A peak pulsed power and slope efficiency of $0.6 mW and $1.3 lW/mA are demonstrated from these thin-film UV LEDs, respectively. For comparison, top-emission UV LEDs are fabricated and back-emission LEDs are shown to extract 50% more light than top-emission ones. V

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

“…A maximum output power of 2.7 mW under CW operation of 273 nm DUV LEDs on ELO AlN templates with the wing region having TDD of 3×10 8 cm -2 has been reported by Hirayama et al [80] By reducing the TDD in AlN layers on sapphire from 10 10 cm −2 to 10 9 cm −2 , output powers of 1mW and about 4mW for 295 nm and 324 nm LEDs, respectively, have been demonstrated by Kueller et al [69] This method has also been applied for growing AlN template on Si (111) substrate, as illustrated in Figure 7. ELO AlN templates on Si (111) substrate with FWHM values of 920 and 780 arcsec for XRD ω-rocking curves from the (0002) and (101 1) reflections, respectively, with simultaneous reduction in crack density have been achieved by Zhang et al [81] A peak pulsed power and slope efficiency of ~0.6 mW and ~1.3 mW/mA, respectively, were demonstrated for 359 nm UV LEDs after removing the Si (111) substrate. In another report, FWHMs of 780 and 980 arcsec for XRD ω-rocking curves from the (0002) and (101 2) reflections, respectively, have been achieved in ELO AlN on Si (111).…”

“…The patterning stripe is along [101 0] AlN. Reprinted from [81], with the permission of AIP publishing.…”

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

“…A maximum output power of 2.7 mW under CW operation of 273 nm DUV LEDs on ELO AlN templates with the wing region having TDD of 3 × 10 8 cm −2 was reported by Hirayama et al [84] By reducing the TDD in AlN layers on sapphire from 10 10 cm −2 to 10 9 cm −2 , output powers of 1 mW and about 4 mW for 295 nm and 324 nm LEDs, respectively, were demonstrated by Kueller et al [73] This method has also been applied for growing AlN template on Si (111) substrate, as illustrated in Figure 7. ELO AlN templates on Si (111) substrate with FWHM values of 920 and 780 arcsec for XRD ω-rocking curves from the (0002) and (101 1) reflections, respectively, with simultaneous reduction in crack density were achieved by Zhang et al [85] A peak pulsed power and slope efficiency of ~0.6 mW and ~1.3 mW/mA, respectively, were demonstrated for 359 nm UV LEDs after removing the Si (111) substrate. In another report, FWHMs of 780 and 980 arcsec for XRD ω-rocking curves from the (0002) and (101 2) reflections, respectively, were achieved in ELO AlN on Si (111).…”

“…DUV LEDs with an emission wavelength of 256-278 nm exhibiting an output power of ~10 μW at a DC injection current of 140 mA without removing the Si substrate [86]. Reprinted from [85], with the permission of AIP publishing.…”

Enhancing the light extraction of AlGaN-based ultraviolet light-emitting diodes in the nanoscale

“…5). 11,35,[55][56][57] The effective refraction index around the interface is thereby between the AlN layer and the substrates (or the templates). The light scattering at the interface reduces the TIR and increases the photons' escape opportunity.…”