講演情報
[11a-S5-1]EQE Increase of 290 nm UVB LED by controlling Ga composition in the AlGaN Electron Blocking Layer (EBL)
〇(D)Hamida Zia1,2, M.Nawaz Sharif1, Hiroyuki Yaguchi2, Hideki Hirayama1 (1.RIKEN Pioneering Research Institute (PRI), 2-1 Hirosawa, Wako, Saitama, Japan, 2.Saitama University, Saitama 338-8570, Japan)
キーワード：
AlxGa1-xN、Electron Blocking Layer (EBL)、Ultraviolet-B (UVB) LEDs
We investigate the deep correlation between the compositional configuration of the AlxGa1-xN electron blocking layer (EBL) and the carrier injection dynamics in ultraviolet-B (UVB) light-emitting diodes emitting at 290 nm. Substantial electron overshoot via over-barrier thermionic emission and quasi-ballistic transport across the EBL, combined with poor hole injection efficiency due to deep acceptor activation energies in high-Al AlGaN, drastically limit the external quantum efficiency (EQE) of deep-UV optoelectronics. To mitigate these bottlenecks, the composition of an 8-nm-thick EBL was precisely engineered during MOCVD growth by varying the trimethylgallium (TMG) flow rate (0 to 3.7sccm) under a constant trimethylaluminum (TMA) flux (30 sccm), systematically altering the rigid band offsets and polarization-induced sheet charges at the heterojunction interfaces. Experimental results revealed that an initial increase in Ga flow rate to 2.0 sccm led to a degradation in performance due to insufficient electron confinement. However, further optimization towards a critical flow rate regime significantly improved device metrics. At an optimized EBL Ga flow rate of 3.5 sccm, the UVB LEDs exhibited a dramatic surge in performance, achieving a peak external quantum efficiency (EQE) of approximately 2.3% and a substantial boost in light output power (LOP) exceeding 15 mW at 180 mA on the bare wafer [1,2]. Electroluminescence (EL) spectra confirmed a sharp, dominant emission peak at 290 nm with negligible parasitic defect peaks, indicating excellent material quality and efficient radiative recombination within the 3-fold Al0.50Ga0.50N/Al0.58Ga0.42N multi-quantum wells (MQWs). This work underscores the leverage of fine-scale energy band engineering within the EBL to overcome intrinsic carrier transport imbalances in AlGaN heterostructures.