Ultra‐Transparent Epitaxy Architecture Enabling High‐Efficiency AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes

ABSTRACT The limited light extraction and electrical inefficiencies in AlGaN‐based deep‐ultraviolet light‐emitting diodes (DUV LEDs) arise from two interrelated bottlenecks: intrinsic optical absorption and poor carrier injection. Here, we present an ultra‐transparent AlGaN epitaxy architecture utilizing a high‐Al‐content n‐Al 0.65 Ga 0.35 N instead of n‐Al 0.45 Ga 0.55 N contact layer and an n + ‐Al 0.55 Ga 0.45 N/p + ‐Al 0.55 Ga 0.45 N ultrathin tunnel junction (UTJ) instead of p‐GaN contact layer. This ensures the bandgaps of p‐ and n‐regions substantially exceed that of the Al 0.45 Ga 0.55 N quantum well, achieving an unprecedented ~90% transmittance (270‐310 nm) and minimizing parasitic absorption. Implementing hybrid pretreatment consisting of Cl 2 plasma repair and N 2 thermal annealing, the specific contact resistivity between Cr/Ti/Al/Ti/Pt/Au metal cathode and high‐Al‐content n‐Al 0.65 Ga 0.35 N contact layer decreases by an order of magnitude. Concurrently, we find that the high ‐reflective Rh metal anode can form a low‐resistance ohmic contact with the n + ‐Al 0.55 Ga 0.45 N/p + ‐Al 0.55 Ga 0.45 N UTJ contact layer. Moreover, light output power improves by 21.6% through optimizing the configuration of the high‐reflective Rh grid anode embedded with Al microdisks. Consequently, the wall‐plug efficiency of the ultra‐transparent epitaxy‐based DUV LEDs reaches 8.2%, 2.1 times that of conventional devices. This ultra‐transparent epitaxy architecture and corresponding optimization strategies establish a transformative paradigm for high‐performance DUV optoelectronic devices, with immediate implications for DUV water purification and biomedical sterilization technologies.