Experimental and simulation studies on temporal evolution of chemically etched Si surface: Tunable light trapping and cold cathode electron emission properties

Abstract

Anisotropic alkaline etching of single crystalline p-Si(100) substrates is carried out for different times (in the range of 30–2400 s). This leads to the formation of randomly distributed pyramidal structures on Si surfaces, as observed from atomic force microscopy (AFM) and scanning electron microscopy images. During early stages of etching, rough surfaces evolve, but for longer etching times, pyramidally textured surfaces (having dimensions in the range of 0.2–2 μm) are formed. The formation of pyramidal structures is explained in light of simulation studies based on the continuum theory of stress-induced morphological instability. The power spectral density plots extracted from the experimental AFM images and the simulated images show that while the correlation length increases for lower etching times, it gets saturated for higher etching times. These facts corroborate well with our experimental results that reveal increasing pyramidal size with etching time. In addition, we study the temporal evolution of antireflection and field emission properties of such pyramidally textured-silicon substrates in line with their potential use in solar cells and moderate level cold cathode electron emission, respectively. For instance, it is interesting to note that surface reflectance of these pyramidally textured surfaces (formed at higher etching times) can be brought down to as low as 0.4% over a broad spectral range, viz., 300–3000 nm. Likewise, the field emission data show that turn-on potential decreases with increasing etching time (e.g., 2.62 V μm−1 for an etching time of 1200 s).