Study of Self-Powered Broadband Photodetection in Textured p-NiO _<i>x</i> /i-MgO/n-Si (p–i–n) Heterojunctions

The growing advancement in high-speed communication and imaging demands photodetectors capable of efficient, broad-band light detection. NiO, a wide-band-gap semiconductor with high absorption and chemical stability, is an ideal material for high-performance photodetection. In this work, we introduce a thin MgO interfacial layer to engineer the n-Si/p-NiOx heterojunction for improving charge transport characteristics. To further enhance absorption and light trapping over a broad wavelength range, we have utilized a micro pyramidal-textured n-Si substrate prepared via chemical wet etching. X-ray Photoelectron Spectroscopy (XPS) confirms the majority of Ni3+ in the polycrystalline NiOx film, signifying a substantial concentration of nickel vacancies that promote p-type conductivity. The band diagram has been designed using XPS and Ultraviolet Photoelectron Spectroscopy (UPS). The band diagram with the MgO layer shows high valence and conduction band offset, which decreases the signal-to-noise ratio. Among all three fabricated samples, Textured-Si/MgO/NiOx has the best performance in terms of responsivity, detectivity, and external quantum efficiency (EQE). The textured device has a maximum responsivity of 1.12 A/W and a 160% EQE for 850 nm light with an illumination intensity of 19.68 mW/cm2 under −2 V bias. Textured-Si/MgO/NiOx exhibits approximately 5 times higher responsivity than Si/MgO/NiOx at 455 and 485 nm. The specific detectivity is approximately 1012 Jones throughout the spectral range in the self-powered mode, demonstrating promising potential for weak-light detection. The device exhibits consistent and precise switching behavior, with rise and fall periods of 0.14 and 0.148 s, respectively, signifying rapid carrier dynamics.