Study of n-ZnO/p-Si (100) thin film heterojunctions by pulsed laser deposition without buffer layer

ZnO/Si heterojunctions were fabricated by growing ZnO thin films on p-type Si (100) substrate by pulsed laser deposition without buffer layers. The crystallinity of the heterojunction was analyzed by high resolution X-ray diffraction and atomic force microscopy. The optical quality of the film was analyzed by room temperature (RT) photoluminescence measurements. The high intense band to band emission confirmed the high quality of the ZnO thin films on Si. The electrical properties of the junction were studied by temperature dependent current–voltage measurements and RT capacitance–voltage (C–V) analysis. The charge carrier concentration and the barrier height (BH) were calculated, to be 5.6 × 1019 cm− 3 and 0.6 eV respectively from the C–V plot. The BH and ideality factor, calculated using the thermionic emission (TE) model, were found to be highly temperature dependent. We observed a much lower value in Richardson constant, 5.19 × 10− 7 A/cm2 K2 than the theoretical value (32 A/cm2 K2) for ZnO. This analysis revealed the existence of a Gaussian distribution (GD) with a standard deviation of σ2 = 0.035 V. By implementing the GD to the TE, the values of BH and Richardson constant were obtained as 1.3 eV and 39.97 A/cm2 K2 respectively from the modified Richardson plot. The obtained Richardson constant value is close to the theoretical value for n-ZnO. These high quality heterojunctions can be used for solar cell applications.

► ZnO/Si heterojunctions are fabricated by pulsed laser deposition without buffers.
► X-ray diffraction confirmed the ZnO film crystallinity.
► Photoluminescence confirmed the optical quality of ZnO thin film.
► Current–voltage analysis shows the presence of barrier inhomogeneities.
► Gaussian distribution is used to explain the barrier inhomogeneity at the interface.