GaN-based semiconductors are promising materials for solid-state optoelectronic applications. However, the strong internal electrostatic field (IEF) along the [0001] direction is a serious problem that harms the efficiency of lighting devices based on GaNbased semiconductors due to the quantum confined Stark effect. Here we theoretically predict a method, reducing the dimensions from bulk to two-dimensional (2D) structures, to fundamentally remove the IEF. After thinning the materials to several nanometers, the wurtzite configuration (with strong IEF) spontaneously transform to the haeckelite (4 | 8) configuration (without IEF) due to the more stable neutral surface in the 4 | 8 configuration. Meanwhile, the 4 | 8 configuration maintain optoelectronic properties comparable to or even better than those of the wurtzite configuration. By carefully analyzing the interaction between 2D GaN and different types of substrates (SiC and graphene), we not only provide clear physical insights for experimental results but also address a "thickness-controlled" vdW epitaxy scheme to experimentally realize the 4 | 8 configuration. We believe that the 4 | 8 configuration without IEF is a prospective material for diverse optoelectronic applications. In addition, we propose a point of view in engineering the properties of GaN-based semiconductors.

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In this work, AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) with AlGaN as the dielectric layers in p+-Al0.55Ga0.45N/AlGaN/n+-Al0.55Ga0.45N polarization tunnel junctions (PTJs) were modeled to promote carrier tunneling, suppress current crowding, avoid optical absorption, and further enhance the performance of LEDs. AlGaN with different Al contents in PTJs were optimized by APSYS software to investigate the effect of a polarization-induced electric field (Ep) on hole tunneling in the PTJ. The results indicated that Al0.7Ga0.3N as a dielectric layer can realize a higher hole concentration and a higher radiative recombination rate in Multiple Quantum Wells (MQWs) than Al0.4Ga0.6N as the dielectric layer. In addition, Al0.7Ga0.3N as the dielectric layer has relatively high resistance, which can increase lateral current spreading and enhance the uniformity of the top emitting light of LEDs. However, the relatively high resistance of Al0.7Ga0.3N as the dielectric layer resulted in an increase in the forward voltage, so much higher biased voltage was required to enhance the hole tunneling efficiency of PTJ. Through the adoption of PTJs with Al0.7Ga0.3N as the dielectric layers, enhanced internal quantum efficiency (IQE) and optical output power will be possible.