A way to reduce leakage current and increase the efficiency of III-Nitride microLEDs via ALD sidewall passivation.
Due to the chemical inertness of III-nitrides semiconductor materials, plasma-based dry etching is widely employed to define the mesa structure of LEDs. Due to the high-energy nature of plasma etching, the sidewall of the LED has defects which result in leakage current and reduction of internal quantum efficiency. There are currently techniques to try to minimize these problems. Sidewall passivation using dielectrics has been demonstrated and used to decrease the leakage current and plasma-enhanced chemical vapor deposition (PECVD) is the common technique for deposition dielectrics to passivate the sidewall. However, as the size of LED diminishes, it is easier for hydrogen to diffuse into LEDs, lowering the efficiency. This results in less light being extracted from the LED. MicroLEDs are used in a number of “Near-eye” display devices, which have very low current in order to avoid retina damage. As a result, microLEDs with very low leakage current are desired.
Researchers at the University of California, Santa Barbara have developed a way to reduce leakage current and increase the efficiency of III-Nitride microLEDs via ALD sidewall passivation. ALD has atomic-scale control on the deposition rate of dielectrics thin film. The dielectric film is sufficient to passivate the sidewall of LEDs and to reduce leakage current for microLEDs. Furthermore, ALD is a hydrogen-free deposition method which prevents the problem of hydrogen passivation, thus increasing the efficiency of the LEDs.