Size-Independent Forward Voltage Micro-LED with an Epitaxial Junction

Conventional tunnel junction micro-LEDs currently face challenges of higher voltage penalties and varied voltage with different device sizes. Unfortunately, size-dependent voltage characteristics limit the applications of micro-LEDs and result in a lack of device reliability. Thus, overcoming the size dependence of the forward voltage in tunnel junction micro-LEDs would increase their potential to meet the demands of next-generation display applications. 

Researchers at the University of California, Santa Barbara have fabricated size-independent forward voltage micro-LEDs with an epitaxial tunnel junction comprised of p+GaN and n+GaN layers. This technology employs n+GaN layers with patterns of holes or vias to provide activation of the p+GaN type layer. The micro-LEDs produced using this approach with a Si doping concentration in the n+GaN layers higher than 1.7 X 10²⁰ cm^-3 demonstrated a forward voltage at 20A cm^-2 that was stable and uniform around 3.4V. Therefore, this technique solves the issue of forward voltage variation in different size tunnel junction micro-LEDs by realizing a size-independent low forward voltage.