By combining microscale-transfer printing with liquid capillary bonding, the authors of this Optics Express demonstrated nanomembranes LEDs on diamond substrates that can exhibit significantly improved performance. Unique to this approach is that, instead of using any adhesion-enhancement layers, a consistent Van der Waals bond is achieved, which leads to very efficient heat dissipation. A. J. Trindade et al. performed detailed fabrication and characterization of micro-scale (100×100 μm2) LEDs on diamond and silica substrates. The surface roughness of the transferred nanomembranes is only ~ 1 nm. For an injection current density of 100 A/cm2, the junction temperature for LEDs on diamond is almost a factor two lower than that on silica (~ 60ºC vs. 120ºC), due to the much higher thermal conductivity of diamond. An optical density of 10 W/cm2 was measured for LEDs transferred on diamond, which is significantly higher than LEDs on silica and Si substrates.
Another benefit associated with the high thermal conductivity of diamond is that the LEDs can be modulated at much higher speed. A maximum electrical-to-optical modulation bandwidth of 154 MHz was measured for LEDs on diamond, enabling an impressive back-to-back data transmission rate of 400 Mbit/s.
With further optimization of the strain distribution in the LED structures, the unique transfer printing technology developed by Trindade et al. can be readily applied for LED arrays with various sizes, thereby providing a viable alternative to achieving high efficiency LEDs for smart lighting, flexible displays, and consumer electronics.
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