To improve the optical and electrical properties of AlGaN-based deep ultraviolet lasers, an inverse-trapezoidal electron blocking layer is designed. Lasers with three different structural electron blocking layers of rectangular, trapezoidal and inverse-trapezoidal structures are established. The energy band, electron concentration, electron current density, P–I and V–I characteristics, and the photoelectric conversion efficiency of different structural devices are investigated by simulation. The results show that the optical and electrical properties of the inverse-trapezoidal electron blocking layer laser are better than those of rectangular and trapezoidal structures, owing to the effectively suppressed electron leakage.

The electron blocking layer (EBL) plays a vital role in blocking the electron overflow from an active region in the AlGaN-based deep-ultraviolet light-emitting diode (DUV-LED). Besides the blocking of electron overflow, EBL reduces hole injection toward the active region. In this work, we proposed a DUV nanowire (NW) LED structure without EBL by replacing it with a compositionally continuous graded hole source layer (HSL). Our proposed graded HSL without EBL provides a better electron blocking effect and enhanced hole injection efficiency. As a result, optical power is improved by 48% and series resistance is reduced by 50% with 4.8 V threshold voltage. Moreover, graded HSL without EBL offer reduced electric field within the active region, which leads to a significant increment in radiative recombination rate and enhancement of spontaneous emission by 34% at 254 nm wavelength, as a result, 52% maximum internal quantum efficiency with 24% efficiency drop is reported.

The design of the active region structures, including the modifications of structures of the quantum barrier (QB) and electron blocking layer (EBL), in the deep ultraviolet (DUV) AlGaN laser diode (LD) is investigated numerically with the Crosslight software. The analyses focus on electron and hole injection efficiency, electron leakage, hole diffusion, and radiative recombination rate. Compared with the reference QB structure, the step-like QB structure provides high radiative recombination and maximum output power. Subsequently, a comparative study is conducted on the performance characteristics with four different EBLs. For the EBL with different Al mole fraction layers, the higher Al-content AlGaN EBL layer is located closely to the active region, leading the electron current leakage to lower, the carrier injection efficiency to increase, and the radiative recombination rate to improve.

The superlattice electron blocking layer (EBL) has been proposed to reduce the electron leakage of the deep ultraviolet light emitting diodes (DUV-LEDs). However, the hole transport is hindered by the barriers of EBL and the improvement of hole injection efficiency still suffers enormous challenges. The superlattice step doped (SLSD) EBL is proposed to improve the hole injection efficiency while enhancing the electron confinement capability. The SLSD EBL enhances the electron confinement capability by multi-reflection effects on the electron wave function. And a built-in electric field towards the active region is generated by superlattice step doping, which facilitates the transport of holes into the multiple quantum wells. The Advaced Physical Model of Semiconductor Devices (APSYS) software is used to simulate the DUV-LEDs with conventional EBL, superlattice EBL, superlattice doped EBL, and SLSD EBL. The results indicate that the SLSD EBL contributes to the increased electron concentration in the multiple quantum wells, the reduced electron leakage in the p-type region, the increased hole injection current, and the increased radiative recombination rate. When the current is 60 mA, the external quantum efficiency of DUV-LED with SLSD EBL is increased to 5.27% and the output power is increased to 13.81 mW. The SLSD EBL provides a valuable reference for solving the problems of serious electron leakage and insufficient hole injection of the DUV-LEDs.

We propose two composition-graded quantum barriers (QBs) to improve the performance of AlGaN-based deep ultraviolet laser diodes (DUV-LDs). The optical and electrical properties of three LDs containing conventional QBs, graded increased QBs, and graded decreased QBs were numerically investigated. It was found that the LDs with graded decreased QBs significantly improved the carrier injection efficiency, raised the carrier concentration in the active region, reduced the carrier leakage, and enhanced the stimulated recombination rate of the LDs. Simulation results showed that, at an 80-mA injection current, the threshold current and threshold voltage were reduced to 29.5 mA and 4.78 V, respectively. The slope efficiency was improved to 2.52 W/A, and the electro-optical conversion efficiency was increased to 52.2%. Compared with the conventional structure of LDs, grading the QBs with decreasing Al-content improved the performance of the LD remarkably, which is essential for the development of DUV-LD.