Novel Composite Substrates for Thin Film AlGaInP-based High Power LEDs

In this paper, the n-side up thin-epilayer, AlGaInP base vertical light-emitting diodes (VLEDs) (light emitting area:
$44\ \mathrm{mil}\times 44\ \mathrm{mil}$
) with three different Si, CIC (Copper Invar Copper) and CuW substrates were obtained by wafer bonding and epilayer transferring technologies due to the poor thermal conductivity (52 W/m-K) and low bandgap (1.42eV) of GaAs substrate, which decreases the characteristics of the LEDs and results in a lower saturation current and low output power. The coefficient of thermal expansion of CIC and CuW substrates are about
$6.1\times 10^{-6}/\mathrm{K}$
and
$6.5\times 10^{-6}/\mathrm{K}$
respectively, which are matched to that GaAs substrate and AlGaInP epilayers. The performance of the packaged CIC LEDs are improved, resulting in a high operational current, a low red shift phenomenon (from 624 to 646 nm for 100 mA to 1 A) and a high output power (300 mW at 1 A) as compare to Packaged CuW LEDs and the variation in light-emitting wavelength of the LEDs made on the Si substrate is larger than that of the CIC substrate. LEDs are made on the CIC substrate can be extended to fabricate high-power thin film LEDs with conventional vertical electrodes.