The junction temperature of high-power LEDs can directly affect the performance and longevity of some LED devices. As the junction temperature rises, a significant loss of output (luminosity) can be expected. The forward voltage of an LED is also dependent on the junction temperature. As the temperature rises, the forward voltage decreases, which can cause excessive current drain on other LEDs in the array. This in-turn leads to thermal runaway conditions and ultimately to the failure of the device. High temperatures can also affect the wavelength of an LED fabricated using gallium arsenide, gallium nitride or silicon carbide.
Bulk thermoelectric (TEC) devices have been used to provide temperature control of LEDs. However, today a major trend in photonics has been the move to smaller form factor, higher power and more integrated, and cheaper packaging in order to enable a lower cost structure and concurrently opening the door for higher volume manufacturing. In the course of this transition, conventional TEC solutions have not kept pace with these needs due to their size and power density limitations.
Thin-film embedded thermoelectric coolers (eTECs) are smaller and thinner than conventional products and show promise for direct integration using industry standard manufacturing methods. In addition, thin film eTECs have demonstrated a heat-flux pumping capacity that far exceeds that provided by traditional bulk TECs. This makes eTECs well suited for high heat density applications. The use of thin films allows for novel implementations of thermoelectric devices, particularly for cooling of high-power LEDs.