# Recent Advances in Black Silicon Surface Modification for Enhanced Light Trapping in Photodetectors
## 4 Black Silicon for Light Trapping in Photodetectors
Figure 7: Responsivity characteristics of the optimized Ti hyper-doped BSi photodetector, illustrating (**a**) the responsivity under various bias voltages; the red dotted line denotes the responsivity of a commercial silicon photodiode (Si PD) under a bias voltage of \(-\)12 V for comparative purposes; (**b**) the corresponding EQE of the titanium hyper-doped BSi photodetector is depicted, with the dotted gray line indicating an EQE value of 100% [79]. Silver-assisted metal-assisted chemical etching (Ag-MACE) significantly improved the performance of multi-crystalline silicon-based photodetectors. [PERSON] et al. demonstrated that the average responsivity of photodetectors with Ag-MACE-modified BSi surfaces substantially increased from 0.64 A/W to 19.24 A/W, largely due to optimized surface nanostructures, which enhanced light trapping and reduced reflectance [24]. In another study, reactive ion etching (RIE) produced hierarchical micro/nanostructures that reduced reflectance to less than 1% across the visible and near-infrared (NIR) spectrum. [PERSON] et al. reported that such structures enhanced the quantum efficiency (QE) of photodetectors to 99% in the visible range, while significantly reducing noise levels [51]. Deep reactive ion etching (DRIE), which forms deep nanostructures, has demonstrated high responsivity values. For instance, BSi photodetectors fabricated through DRIE showed excellent responsivity of up to 40 A/W at 950 nm, with a noise equivalent power (NEP) of 10-14 W/Hz0.5 [54]. Moreover, laser ablation has been employed to enhance photodetector performance, particularly in the infrared region. [PERSON] et al. demonstrated that Se-doped BSi photodetectors, created using laser ablation, exhibited broadband absorption from 400 nm to 2200 nm. These photodetectors reached a peak quantum efficiency of 96%, with a responsivity exceeding 10 A/W in the near-infrared range, and reduced dark current to below 783 nA at a bias of \(-\)5 V [23]. Table 3 presents a comparative analysis focused on critical metrics: light absorption efficiency, fabrication cost, process complexity, and scalability to provide clearer insights into the advantages and disadvantages of various BSi surface modification techniques. \begin{table}
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**Study Objectives** & **Methodologies** & **Results** & **Applications** & **Ref.** \\ \hline Reviewing recent progress in Si/2 DM photodetectors & By focusing on the ultrabroad operation wavelength range and flexible integration, particularly in the NIR to MIR wavelength band & Significant advancements have been realized, encompassing approximately 100 GHz high-bandwidth M-G-M PDs. Photodetectors based on the ultra-high sensitivity of the PG effect. A number of representative wafer-scale image sensors constructed from Si/2 DM PDs, along with their corresponding arrays, have also been demonstrated. & Integrating 2 DMs with Si microelectronics and photodetectors based on the ultra-high compatibility technologies technological pathway for developing high-performance, cost-effective PDs, which may significantly influence the advancement of next-generation optoelectronic integrated circuits. & Integrating 2 DMs with Si microelectronics and photodetectors based on the ultra-high compatibility technologies technologies & [76] \\ To enhance the capturing of the sub-bandgap light and create a photocurrent & By preparing Si photodetector based on a BSi/ Ag NPs Schottky junction & 3.5 & 3.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._Each technique offers distinct benefits and trade-offs, making them more or less suitable for different applications. In addition, each technique offers specific advantages depending on the application. For instance, MACE is highly scalable and cost-effective, making it suitable for large-scale photovoltaic cell production. In contrast, RIE and DRIE provide more precise control over surface structures but come with higher complexity and cost.