Ultralow Optical and Electrical Losses via Metal‐Assisted Chemical Etching of Antireflective Nanograss in Conductive Mesh Electrodes

Abstract

Various types of anti‐reflective technologies are capable of increasing the light absorption of optical devices. The electrical conductivity of the collected carriers must also be increased for efficient photoelectric conversion. However, increasing the front electrode area reduces the amount of light absorption, causing shading and resistive losses to conflict in front‐illuminated devices. In this study, a low‐reflectance surface and high‐conductance electrode for Schottky photodiodes are fabricated using metal‐assisted chemical etching (MacEtch). Si nanograss (SiNG) and Ag‐mesh formed via MacEtch serve as a subwavelength surface and buried electrodes, respectively. SiNG increases light absorption without causing shading loss, while the buried Ag‐mesh considerably improves electrical conductivity. The SiNG/Ag‐mesh structure exhibits a solar weighted reflectance of 1.20% and a sheet resistance of 5.48 Ω □−1. The SiNG/Ag‐mesh Schottky photodiode exhibits an external quantum efficiency of 89.5% at a wavelength of 860 nm and an internal photoemission effect in the sub‐band gap. The self‐organized SiNG/Ag‐mesh, fabricated through a simple wet‐etching method, simultaneously addresses the issues of optical and electrical losses, enabling the application of this technique to a wide range of optoelectronic devices.

Excellent Responsivity and Low Dark Current Obtained With Metal-Assisted Chemical Etched Si Photodiode

“…Nevertheless, the comparison indicates that there is still room for improvement in the performance of MACE photodiodes. Indeed, as reported in the literature [27], even lower reflectance should be achievable by MACE. Likewise, as seen earlier in Fig.…”

“…While MACE has previously been applied to Schottky photodiodes [26], [27], it is well known that they always suffer from high dark current and, consequently, have limited sensitivity. For instance, Zhang et al [26] have recently reported a high-responsivity MACE Si Schottky photodiode; however, the achieved dark current density is as high as 130 nA cm −2 at −1-V bias, which cannot compete with commercial Si photodiodes (typically <10 nA cm −2 ).…”

Catalytic nickel silicide as an alternative to noble metals in metal-assisted chemical etching of silicon

“…Simultaneously, the etched surface and metal catalyst maintain contact throughout the etching process. MACE has been used in various fields such as electronics, 17,18 optoelectronics, [19][20][21] and energy harvesting. [22][23][24] Although MACE has some advantages over dry etching, the current technique cannot be utilized in the complementary metal oxide semiconductor (CMOS) process because of the use of noble metals.…”

Anisotropic Charge Transport Enabling High‐Throughput and High‐Aspect‐Ratio Wet Etching of Silicon Carbide

“…The method can be readily extended to fabricate novel wide bandgap semiconductor structures and devices. [32][33][34][35][36]…”