Low-Frequency 1/<i>f</i> Noise and Barrier Height Inhomogeneity in Topological Insulator-Based Photodetectors

Topological insulators (TIs) with symmetry-protected surface states offer exciting opportunities for next-generation photonic and optoelectronic device applications. The heterojunctions of TIs and semiconductors (e.g., Si and Ge) have been observed to exhibit excellent photoresponsive characteristics. However, the signals and their processing speed are often hindered by large low-frequency 1/<i>f</i> noise, necessitating an in-depth study of 1/<i>f</i> noise for effective realization and commercialization. Here, we report the optoelectronic response and 1/<i>f</i> noise characteristics of a p-n diode fabricated using the topological insulator Bi₂Se₃ and silicon for potential photodetector applications. Through meticulous temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements, we ascertain crucial parameters such as barrier height, ideality factor, and reverse saturation current of the photodetector. The low-frequency 1/<i>f</i> conductance noise spectra suggest a significant presence of trap states influencing the optoelectronic transport properties. The forward noise characteristics exhibit typical 1/<i>f</i> features, with a unislope across four decades of frequency, suggesting a homogeneous distribution of barrier height. The detector photocurrent exhibits sublinear power-law scaling with laser power, which pertains to recombination effects and topological surface states. The hybrid heterojunction demonstrates an excellent photoresponse and reasonably low 1/<i>f</i> noise, making it promising for room-temperature visible photodetector applications.