Investigation of AlGaN-based deep-ultraviolet light-emitting diodes with composition-varying AlGaN multilayer barriers

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes

“…For In x Ga 1− x N/GaN based visible LEDs, it has been widely admitted that the holes are strongly accumulated in the quantum well close to the p-EBL side [ 11 ]. However, the hole distribution across the active region shows different spatial profiles for III-nitride based DUV LEDs according to reports by different groups [ 24 , 68 , 72 , 81 , 82 , 83 , 84 ], e.g., the highest hole concentration is not always found in the quantum well closest to the p-EBL [ 68 , 82 ]. Tsai et al attribute the interesting observations to the reduced valence band offset for the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells, which therefore is beneficial for the hole transport across the MQW region [ 82 ], i.e., the valence band offset is 0.185 eV for the Al 0.55 Ga 0.45 N/Al 0.72 Ga 0.28 N quantum wells of Tsai et al and 0.210 eV for the In 0.15 Ga 0.85 N/GaN quantum wells with the ~450 nm emission wavelength [ 11 ], respectively.…”

“…Tsai et al attribute the interesting observations to the reduced valence band offset for the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells, which therefore is beneficial for the hole transport across the MQW region [ 82 ], i.e., the valence band offset is 0.185 eV for the Al 0.55 Ga 0.45 N/Al 0.72 Ga 0.28 N quantum wells of Tsai et al and 0.210 eV for the In 0.15 Ga 0.85 N/GaN quantum wells with the ~450 nm emission wavelength [ 11 ], respectively. Till now, various conduction band offset/valence band offset ratios ( ΔE C / ΔE V ) are assumed when calculating the carrier transport within the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells, e.g., 70/30 [ 81 , 83 , 84 , 85 ], 65/35 [ 68 , 82 ] and 50/50 [ 24 , 72 ]. We agree to the point proposed by Tsai et al, since we find that the hole concentration in quantum well closest to the p-EBL becomes high if the ΔE C /ΔE V of 50/50 is adopted.…”

“…Although a larger valence band offset (i.e., ΔE C /ΔE V = 50/50) is suggested for AlGaN/AlGaN interface [ 16 ], it seems that the hole distribution in the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells is much more uniform than that in the In x Ga 1− x N/GaN based quantum wells. In addition, the quantum barrier for DUV LEDs is also AlGaN based, for which the AlN composition can be optimized and this will provide more freedom in further modifying the hole distribution within the active region [ 84 ].…”

Study of Deep Ultraviolet Light-Emitting Diodes with a p-AlInN/AlGaN Superlattice Electron-Blocking Layer

“…11 In order to reduce the polarization-induced electrostatic field within the quantum wells, Yin et al employed composition-varying AlGaN multilayer barriers to design AlGaN-based DUV LEDs. 12 Gao et al studied polarization-doped AlGaN UV LEDs to reduce the polarization effect of DUV LEDs. 13 Shen et al adopted Al content-graded AlGaN barriers to design AlGaN-based UV LEDs, 14 which contributes to less electron leakage and better hole injection efficiency.…”

Improving Performance of Algan‐Based Deep‐Ultraviolet Light‐Emitting Diodes by Inserting a Higher Al‐Content Algan Layer Within the Multiple Quantum Wells

“…In addition, structure designs are proven to play a very important role in improving performance of AlGaN‐based DUV‐LEDs, such as staggered multi‐quantum wells (MQWs), asymmetric coupled MQWs, and gradient composition AlGaN barrier . Besides, inserted single spike barrier and composition‐varying AlGaN multilayer barriers also present a positive impact on the performance improvement.…”