Investigation of nanocrystalline Pbs/n-Si heterostructures for optoelectronic applications

The nano-crystalline PbS/n-Si heterostructure was studied using photocurrent spectra, I–V and C–V characteristics and admittance spectroscopy. The frequency dependent junction capacitance and conductance measurements show the presence of two contributions: first, a defect related mechanism which we attribute to a deep trap level with a large cross-section in nano-crystals with smaller sizes around 5 nm at the interface with Si and a second mechanism with an activation energy of about 250 meV, attributed to carrier transport in relatively large PbS grains of about 15 nm in size.