Ultra-wide bandgap (UWBG) semiconductors have great potential for high-power electronics, radio frequency electronics, deep ultraviolet optoelectronic devices, and quantum information technology. Recently, the two-dimensional UWBG GaPS4 was first applied to the solar-blind photodetector in experiments, which was found to have remarkable performance, such as high responsivity, high quantum efficiency, etc., and promising applications in optoelectronic devices. However, the knowledge of monolayer (ML) GaPS4 for us is quite limited, which hinders its design and application in optoelectronic devices. Here, we focus on the properties of electronic structure and intrinsic defects in ML GaPS4 by first-principles calculations. We confirmed that the fundamental gap of ML GaPS4 is 3.87 [Formula: see text], while the optical gap is 4.22 [Formula: see text]. This discrepancy can be attributed to the inversion symmetry of its structure, which limits the dipole transitions from valence band edges to conduction band edges. Furthermore, we found that intrinsic defects are neither efficient p-type nor n-type dopants in ML GaPS4, which is consistent with experimental observations. Our results also show that if one expects to achieve p-type ML GaPS4 by selecting the appropriate dopant, P-rich conditions should be avoided for the growth process, while for achieving n-type doping, S-rich growth conditions are inappropriate. This is because due to the low strain energy, [Formula: see text] has very low formation energy, which leads to the Fermi levels ([Formula: see text]) pinning at 0.35 [Formula: see text] above the valence band maximum and is not beneficial to achieve p-type ML GaPS4 under the P-rich conditions; the large lattice relaxation largely lowers the formation energy of [Formula: see text], which causes the [Formula: see text] pinning at 0.72 [Formula: see text] below the conduction band minimum and severely prevents ML GaPS4 from being n-type doping under the S-rich conditions. Our studies of these fundamental physical properties will be useful for future applications of ML GaPS4 in optoelectronic devices.

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二维超宽带隙半导体中基本和光学间隙与天然缺陷之间差异的起源：硫代磷酸镓

超宽带隙（UWBG）半导体在大功率电子、射频电子、深紫外光电子器件和量子信息技术等方面具有巨大潜力。最近，二维 UWBG GaPS4个在实验中首次应用于日盲光电探测器，发现其具有高响应度、高量子效率等显着性能，在光电器件中具有广阔的应用前景。然而，单层 (ML) GaPS 的知识4个对我们来说是相当有限的，这阻碍了它在光电器件中的设计和应用。在这里，我们重点关注 ML GaPS 中的电子结构和本征缺陷的特性4个通过第一性原理计算。我们确认了 ML GaPS 的基本差距4个为3.87 [公式：见文]，而光学间隙为4.22 [公式：见文]。这种差异可归因于其结构的反转对称性，这限制了从价带边缘到导带边缘的偶极子跃迁。此外，我们发现本征缺陷在 ML GaPS 中既不是有效的 p 型掺杂剂也不是 n 型掺杂剂4个，这与实验观察结果一致。我们的结果还表明，如果希望实现 p 型 ML GaPS4个通过选择合适的掺杂剂，生长过程应避免富P条件，而要实现n型掺杂，富S生长条件是不合适的。这是因为由于应变能低，[公式：见文]具有非常低的形成能，这导致费米能级（[公式：见文]）固定在价带最大值上方 0.35 [公式：见文]并且不利于实现p型ML GaPS4个在富磷条件下；大的晶格弛豫大大降低了[公式：见文本]的形成能，这导致[公式：见文本]钉扎在导带最小值以下 0.72 [公式：见文本]，严重阻碍了 ML GaPS4个在富硫条件下被 n 型掺杂。我们对这些基本物理特性的研究将有助于 ML GaPS 的未来应用4个在光电器件中。