# Recent Advances in Black Silicon Surface Modification for Enhanced Light Trapping in Photodetectors
## 4 Black Silicon for Light Trapping in Photodetectors  
Photodetectors play a crucial role in a varied range of technologies, including sensing and optical communication devices. However, typical Si-based photodetectors are constrained by their inherent limitations in light absorption, suggesting BSi as a ground-breaking solution to this challenge. As the BSi features a surface textured at the microscopic level, such a unique structure is the key to unlocking significantly improved light-trapping ability within the material. By enabling more effective light trapping, BSi-based photodetectors can achieve more excellent light absorption, leading to enhanced sensitivity and overall performance. This section discusses recent works on BSi-based photodetectors and explores the potential of BSi surfaces to improve photodetector technology. To implement BSi and increase the performance of the photodetector, [PERSON] et al. were able to extract high peak photoresponsivity exceeding 10 A/W, as seen in Figure 4a, high optical detection, which is greater than \(2\times 10^{12}\) Jones (1 Jones = 1 cm Hz\({}^{1/2}\)/W) (see Figure 4b) through the temperature cycle (from 10 to 300 K), and broadband detection sensitivity from 400 to 1200 nm by using the femtosecond pulsed laser method to create BSi structure [70]. Moreover, the heterogeneity of the BSi layer, coupled with the presence of lattice defects, resulted in an increased noise level in devices fabricated utilizing BSi. [PERSON] et al. successfully designed and fabricated a lateral heterojunction at the interfaces of BSi and Si to mitigate leakage current [71]. Through this lateral structure, the BSi-based photodetector was able to effectively reduce dark current to 783 nA under a bias of \(-\)5 V, as presented in Figure 5, representing a substantial decrease in magnitude compared to vertical structures. Simultaneously, at the same bias voltage, they achieved a remarkable external quantum efficiency (EQE) of 371% and a photo-to-dark current ratio of 155. [PERSON] et al. successfully conducted a comparative analysis of BSi-based photodetectors and both planar silicon-induced-junction and planar silicon-pn-junction photodetectors, with the objective of evaluating the contributions derived from the characteristics of both BSi and semiconductor junctions [72]. They assessed the EQE of all the junctions and determined that an induced junction containing BSi surface and aluminum oxide (Al\({}_{2}\)O\({}_{3}\)) demonstrates substantial resilience to radiation-induced proton and electron exposure degradation. While the pn-junction photodetectors, which are passivated with silicon dioxide (SiO\({}_{2}\)), demonstrated considerable deterioration in their UV responsivity following exposure to electron irradiation. The scientific community's standard for room temperature broadband photo-response via a single device remains precedent. A variety of methodologies have been utilized in this domain, including comprehensive nanoscale patterning, the patterning and growth of heterostructures, and the modulation of band gaps through field induction. Nevertheless, the photo-response at room temperature of current photodetectors remains confined to a specific segment of the electromagnetic spectrum. [PERSON] et al. successfully demonstrated the detection of broadband light in the visible to mid-infrared (MIR) range at room temperature using a lateral heterojunction-based photodetector composed of nanolayered black arsenic (BAs)-Si (BAs-Si) [73]. This broad spectral responsiveness was achieved by capitalizing on the appropriate essential band gaps of BAs and Si. Subsequently, the mechanical exfoliation technique was used to create the photodetectors of BAs on a Si-on-insulator (SOI) substrate.