  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, Ge) have
been observed to excellent photo-responsive characteristics. However, the
realization of high-frequency operations in these heterojunctions can be
hindered by unwanted 1/f (or Flicker) noise and phase noise. Therefore, an
in-depth understanding of 1/f noise figures becomes paramount for the effective
utilization of such materials.Here we report optoelectronic response and 1/f
noise characteristics of a p-n diode fabricated using topological insulator,
Bi2Se3 and silicon for potential photo-detector. Through meticulous
temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V)
measurements, we ascertain crucial parameters like barrier height, ideality
factor, and reverse saturation current of the photodetector. The low-frequency
1/f conductance noise spectra suggest a significant presence of trap states
influencing the optoelectronic transport properties. The forward noise
characteristics exhibit typical 1/f features, having a uni-slope across four
decades of frequency, suggesting a homogeneous distribution of barrier height.
The spectral and photocurrent-dependent responses show the power law behavior
of noise level on photon flux. The hybrid heterojunction demonstrates excellent
photo-response and reasonably low noise level, promising signatures for the
room-temperature visible photodetector applications.
