Optical Characterization of GaN-Based Vertical Blue Light-Emitting Diodes on P-Type Silicon Substrate

Abstract

Fabricating GaN-based light-emitting diodes (LEDs) on a silicon (Si) substrate, which is compatible with the widely employed complementary metal–oxide–semiconductor (CMOS) circuits, is extremely important for next-generation high-performance electroluminescence devices. We conducted a systematic investigation of the optical properties of vertical LEDs, to reveal the impacts of the manufacturing process on their optical characteristics. Here, we fabricated and characterized high-efficiency GaN-based LEDs with integrated surface textures including micro-scale periodic hemispherical dimples and nano-scale random hexagonal pyramids on a 4 inch p-type Si substrate. The highly reflective Ag/TiW metallization scheme was performed to decrease downward-absorbing light. We demonstrated the influence of transferring LED epilayers from a sapphire substrate onto the Si substrate on the emission characteristics of the vertical LEDs. The removal of the sapphire substrate reduced the adverse impacts of the quantum-confined Stark effect (QCSE). The influence of integrated surface textures on the light extraction efficiency (LEE) of the vertical LEDs was studied. With the injection current of 350 mA, vertical LEDs with integrated surface textures demonstrated an excellent light output power of 468.9 mW with an emission peak wavelength of 456 nm. This work contributes to the integration of GaN-based vertical LEDs into Si-based integrated circuits.

Substrate Effects on the Electrical Properties in GaN-Based High Electron Mobility Transistors

“…In this perspective, the device transfer technology using the laser lift-off (LLO) technique, which is widely applied for GaN-based light-emitting diodes to improve light extraction ratio, thermal dissipation, and operating current [18][19][20][21] was studied in GaNbased HEMTs [14,22,23]. GaN-based HEMTs were fabricated on sapphire substrates and separated using the LLO technique.…”

Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates

“…On the other hand, Si substrates are the lowest cost and they provide opportunities for optoelectronic integration. Thus, it is very important to insert III-Nitride DBRs in situ between the LED active layer and the Si substrate, since the light emitted downwards would be reflected by the DBR and prevented from being absorbed by the opaque Si substrate [24]. Then, the luminous efficiency of LEDs on Si substrates can be improved.…”