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 (μ‐LEDs) on Si substrates are thoroughly investigated and compared with its counterpart on sapphire substrate. Noticeable optical crosstalk is invariably present in GaN‐on‐sapphire devices as the thick transparent sapphires beneath the μ‐LEDs serve as optical waveguides to favor lateral propagation of the emitted light, eventually causing unwanted noise signals. μ‐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 μ‐LED applications. Light intensity maps illustrating crosstalk performances of GaN‐on‐sapphire μ‐LEDs with backsides coated with (left) Al mirror and (middle) black paint, and (right) GaN‐on‐Si μ‐LED, captured by confocal microscopy.