Optical crosstalk analysis of micro-pixelated GaN-based light-emitting diodes on sapphire and Si substrates

With the aid of depth-resolved confocal microscopy, the optical crosstalk phenomenon in GaN-based micro-pixel light-emitting diodes (m-LEDs) on Si substrates are thoroughly investigated and compared with its counterpart on sapphire substrate. Noticeable optical crosstalk is invariably present in GaNon-sapphire devices as the thick transparent sapphires beneath the m-LEDs serve as optical waveguides to favor lateral propagation of the emitted light, eventually causing unwanted noise signals. m-LEDs adopting the GaN-on-Si platform can effectively suppress unwanted optical crosstalk and sustain superior performance at different injection currents, which are well-suited for a wide range of m-LED applications. Light intensity maps illustrating crosstalk performances of GaN-on-sapphire m-LEDs with backsides coated with (left) Al mirror and (middle) black paint, and (right) GaN-on-Si m-LED, captured by confocal microscopy.