Vertical InGaN light-emitting diodes with a sapphire-face-up structure

Abstract

Vertical GaN-based light-emitting diodes (LEDs) were fabricated with a Si substrate using the wafer-bonding technique. Lapping and dry-etching processes were performed for thinning the sapphire substrate instead of removing this substrate using the laser lift-off technique and the thinning process associated with the wafer-bonding technique to feature LEDs with a sapphire-face-up structure and vertical conduction property. Compared with conventional lateral GaN/sapphire-based LEDs, GaN/Si-based vertical LEDs exhibit higher light output power and less power degradation at a high driving current, which could be attributed to the fact that vertical LEDs behave in a manner similar to flip-chip GaN/sapphire LEDs with excellent heat conduction. In addition, with an injection current of 350 mA, the output power (or forward voltage) of fabricated vertical LEDs can be enhanced (or reduced) by a magnitude of 60% (or 5%) compared with conventional GaN/sapphire-based LEDs.

Improved heat dissipation in gallium nitride light-emitting diodes with embedded graphene oxide pattern

“…This approach has a significant advantage in terms of substrate heat dissipation 3 , which is a key for the realization of bright and durable LEDs. However, there also exist several long-standing drawbacks such as low device yield, difficulty in separating the epitaxial layers from the singlecrystal substrate, complicated fabrication processes and so on 7,9,13 . Consequently, the search for the development of an effective heat dissipation means is intensifying to realize a robust solid-state lighting device with long life time.…”

Heat and fluid flow in high-power LED packaging and applications

“…Thus τy depends on the particle volume fraction f. The analytical models [153][154][155][156][157] show that kTIM of particle-filled TIM also depends on f according to Eqs. (7) and (8). Many studies [128,[180][181][182][183] have found that, as shown in Fig.…”

“…where C and M are 1.31×10 -4 and 0.166, respectively [130]. This model shows that BLT of particle-filled TIM depends on the yield stress of the material τy and the applied pressure P. τy can be expressed as [179]   (8) where A and fm are the constant and maximum particle volume fraction, respectively. Thus τy depends on the particle volume fraction f. The analytical models [153][154][155][156][157] show that kTIM of particle-filled TIM also depends on f according to Eqs.…”

Improvement of light quality by ZrO_2 film of chip on glass structure white LED

“…However, the poor thermal conductivity and insulating substrate pose difficulties in application [4]. To deal with this issue, flip-chip technology becomes popular in recent years because it can induce high light-extraction efficiency and good heat dissipation [5][6][7]. In the flip-chip scheme, an increase of output power can be observed due to the reflector at the bottom and direct bonding of the contact pads which can reduce the shadowing effect [8,9].…”