Probing Boron Vacancy Complexes in h-BN Semi-Bulk Crystals Synthesized by Hydride Vapor Phase Epitaxy

Hexagonal BN (h-BN) has emerged as an important ultrawide bandgap (UWBG) semiconductor (Eg~6 eV). The crystal growth technologies for producing semi-bulk crystals/epilayers in large wafer sizes and understanding of defect properties lag decades behind conventional III-nitride wide bandgap (WBG) semiconductors. Here we report probing of boron vacancy (VB)-related defects in freestanding h-BN semi-bulk wafers synthesized by hydride vapor phase epitaxy (HVPE). A photocurrent excitation spectroscopy (PES) was designed to monitor the transport of photoexcited holes from deep-level acceptors. A dominant transition line at 1.66 eV with a side band near 1.62 eV has been directly observed, which matches well with the calculated energy levels of 1.65 for the VB-H deep acceptor in h-BN. The identification of VB complexes via PES measurement was further corroborated by the temperature-dependent dark resistivity and secondary ion mass spectrometry measurements. The results presented here suggested that it is necessary to focus on the optimization of V/III ratio during HVPE growth to minimize the generation of VB-related defects and to improve the overall material quality of h-BN semi-bulk crystals. The work also provided a better understanding of how VB complexes behave and affect the electronic and optical properties of h-BN.

六方氮化硼（h - BN）已成为一种重要的超宽带隙（UWBG）半导体（带隙约为6 eV）。用于生产大尺寸晶圆的半块状晶体/外延层的晶体生长技术以及对缺陷性质的了解，比传统的III族氮化物宽带隙（WBG）半导体落后数十年。在此，我们报道了对通过氢化物气相外延（HVPE）合成的独立h - BN半块状晶圆中硼空位（VB）相关缺陷的探测。设计了一种光电流激发光谱（PES）来监测深能级受主的光激发空穴的传输。直接观察到在1.66 eV处有一条主跃迁线，在1.62 eV附近有一个边带，这与h - BN中VB - H深受主计算出的1.65 eV能级吻合良好。通过温度相关的暗电阻率和二次离子质谱测量进一步证实了通过PES测量对VB复合物的识别。这里给出的结果表明，有必要在HVPE生长过程中关注V/III比的优化，以尽量减少VB相关缺陷的产生，并提高h - BN半块状晶体的整体材料质量。这项工作还更好地理解了VB复合物的行为以及它们如何影响h - BN的电学和光学性质。