High-Power GaN-Based Light-Emitting Diodes Using Thermally Stable and Highly Reflective Nano-Scaled Ni–Ag–Ni–Au Mirror

Abstract

In this study, we have fabricated the high-power GaNbased vertical light-emitting diodes (VLEDs) by exploiting a thermally stable nano-scaled Ni-Ag-Ni-Au mirror. After being treated at 600 C for 1 min in air ambient, the nano-scaled Ni-Ag-Ni-Au (5/2000/1000/2000 Å) mirror shows the specific contact resistance of cm and its reflectivity has increased from 89.5% to 93.0%. The increment in the reflectivity is due to the diffusion of Ni contact layer into Ag layer. Moreover, the reflectivity of the mirror has hardly deteriorated even after the wafer was thermally bonded with graphite substrate at 320 C for 5 min, meaning that the proposed mirror is thermally reliable. The light output power of the nano-scaled VLED (Chip size: 1 1 mm ) with thermal treatment at 600 C for 1 min is enhanced by 8% as compared to one without thermal treatment at an injection current of 350 mA. To our knowledge, our nano-scaled mirror has the highest reflectivity among other Ag-based multilayered reflectors, and thus it is a promising candidate for high-performance VLED. Index Terms-GaN, light-emitting diodes (LEDs), light output power, thermally stable mirror, wafer bonding.

High-Efficiency InGaN/GaN Quantum Well-Based Vertical Light-Emitting Diodes Fabricated on β-Ga2O3 Substrate

“…The structure of the VLED (schematic shown in Figure a), allows light to be emitted through the n-GaN and substrate layers using p-contact (Ag/Au/Ti/Au) as a reflective mirror, which helps to increase the light extraction efficiency (LEE) of the VLED . In addition, the heat generation can be minimized compared to lateral injection LED because of the vertical current distribution and high conductivity of the substrate. , We analyzed the structural quality of the InGaN/GaN MQW VLED using high-resolution imaging with STEM in combination with spatially resolved EDX spectroscopy.…”

Epitaxy of III-Nitrides on β-Ga2O3 and Its Vertical Structure LEDs

“…Due to the high transparency of β-Ga 2 O 3 substrate, the backside emission from β-Ga 2 O 3 is allowed. Finally, the highly reflective p-electrode that covers the whole area and the n-electrode with small area ratio are deposited on p-GaN layer and n-Ga 2 O 3 , respectively, which can enhance the light extraction efficiency [135]. It is worth noting that there is an inversely proportional relationship between transmittance and conductivity of β-Ga 2 O 3 .…”

Decoupling contact and mirror: an effective way to improve the reflector for flip-chip InGaN/GaN-based light-emitting diodes

“…However, the light extraction efficiency is still one of the most critical obstacles which prevents further improvement of the LED efficiency [2,3]. For flip-chip LEDs, the reflector on p-GaN is essential to improve the light extraction efficiency since light is reflected by the mirror and emitted out from the backside of LEDs [4,5].…”