Radiative and Auger Recombination Constants and Internal Quantum Efficiency of (0001) AlGaN Deep‐UV Light‐Emitting Diode Structures

Abstract

A semiempirical model accounting for hole localization by composition fluctuations is applied to estimate the radiative and Auger recombination constants in (0001) AlGaN quantum wells serving as active regions of deep‐ultraviolet (UV) light‐emitting diodes (LEDs). The model is preliminarily calibrated using the directly measured hole localization lengths in Al0.25Ga0.75N alloys and quantum wells. The recombination constants are found to vary nonmonotonously with the alloy composition/emission wavelength. Device simulations combined with the estimated recombination constants enable identification of major factors limiting the internal quantum efficiency of the LED structures: competition of various recombination channels and electron leakage through the electron‐blocking layer at wavelengths longer and shorter than ≈240 nm, respectively. Comparison of the predicted recombination constants with the data available for bulk AlGaN alloys and Al0.45Ga0.55N/AlN quantum wells is done.

Optical Quality and Stimulated Emission of Molecular Beam Epitaxy Grown AlGaN in the Deep Ultraviolet

“…to be %8.0 Â 10 À11 cm 3 s À1 . [41,42] Using this B value, the best fitting gives A ¼ 5.8 Â 10 8 s À1 and C ¼ 3.1 Â 10 À30 cm 6 s À1 . The calculated IQE as a function of n is shown in Figure 3.…”

“…Moreover, the large C coefficient might be attributed to carrier delocalization, Auger recombination, and other effects. [41,42] To examine if there is any light amplification of the AlGaN/ AlN DH, the as-grown wafer was further pumped by the 266 nm laser. The solid and dashed curves in Figure 4a represent the transverse-electric (TE)-and transverse-magnetic (TM)-polarized light emission spectra, respectively.…”

“…Recent comparative studies on the recombination coefficients between the thick AlGaN epilayers and QWs suggest an Al‐content‐dependent B coefficient; and for thick AlGaN epilayers emitting at around 295 nm, the B coefficient is suggested to be ≈8.0 × 10 −11 cm 3 s −1 . [ 41,42 ] Using this B value, the best fitting gives A = 5.8 × 10 8 s −1 and C = 3.1 × 10 −30 cm 6 s −1 . The calculated IQE as a function of n is shown in Figure 3 .…”

“…Moreover, the large C coefficient might be attributed to carrier delocalization, Auger recombination, and other effects. [ 41,42 ]…”

Monolayer-Scale GaN/AlN Multiple Quantum Wells for High Power e-Beam Pumped UV-Emitters in the 240–270 nm Spectral Range

“…An additional decrease in the output UVC power occurs with an increase in the Al content due to the transition from TE-to TM-dominant polarization mode of the output radiation, which has much lower extraction efficiency through the c-plane [9,10]. In addition, a higher Auger recombination and carrier leakage lead to a further deterioration in the efficiency of UV LEDs at high injection currents [11,12]. Finally, the achievement of high values of pand n-type conductivity in Al-rich AlGaN layers should be called, perhaps, the most acute and difficult problem for UVB and UVC LEDs [13].…”