Activation of P-Type Layers of Tunnel Junctions in Micro-LEDs
Tech ID: 32270 / UC Case 2021-551-0
P-type gallium nitride (p-GaN) is difficult to contact electrically and has a low hole concentration and mobility in conventional commercial III-nitride LEDs. This means that p-GaN cannot be used as a current spreading layer and that traditional p-contacts will add significant voltage to devices. Despite these inherent problems, all commercial light emitting devices utilize traditional p-contacts and materials other than p-GaN for current spreading, which typically involves a high barrier for tunneling. Unfortunately, current approaches to reduce the tunneling barrier are associated with losses, either in terms of voltage or resistance increases, or optical losses in the final device performance. These penalties exist even in smaller LED devices such as mini-LEDs and micro-LEDs.
Researchers at the University of California, Santa Barbara have fabricated low forward voltage micro-LEDs with an epitaxial tunnel junction comprised of p+GaN, an InxAlyGazN insertion layer, and n+GaN layers grown using metalorganic chemical vapor deposition (MOCVD). The InxAlyGazN insertion layer offers a smaller energy bandgap than the GaN layers, which works to reduce the depletion width of the tunnel junctions and increase the tunnel probability. Tunnel junction micro-LEDs with an n-type and p-type InxAlyGazN insertion layer demonstrated a very stable low forward voltage at 20A cm-2. Therefore, fabrication of micro-LEDs with low forward voltage is achieved, increasing the potential for next-generation display applications.
- Low forward voltage
- Reduced tunnel junction depletion width
- Increased tunnel probability