Enhancement of GaN-Based Light-Emitting Diodes Transferred From Si (111) Substrate Onto Electroplating Cu Submount With TiO$_{2}$/SiO$_{2}$–Al Omnidirectional Reflector

In this paper, crack-free InGaN/GaN multiple quantum wells (MQWs) light-emitting diodes (LEDs) were transferred from Si (111) substrate onto the electroplating Cu submount, with inserting a 5-pair TiO
$_{2}$
/SiO
$_{2}$
omnidirectional reflector (ODR) and an Al mirror, defined as TiO
$_{2}$
/SiO
$_{2}$
–Al ODR. The reflectivity in the blue spectral range of the TiO
$_{2}$
/SiO
$_{2}$
–Al ODR was as high as 97%. The current–voltage (I–V) characteristics showed no obvious degradation of electrical properties for the ODR-based LED on Cu. In comparison to conventional LEDs on Si without ODRs, the light output of ODR-based LEDs on Cu was enhanced by 59.3% at a driving current of 350 mA. The improvement is mainly attributed to the following factors: the removal of the opaque Si substrate, the inserting of the high-reflectivity TiO
$_{2}$
/SiO
$_{2}$
–Al ODR, and the transfer onto the Cu submount with better thermal conductivity.