Angular reflectivity of a ZnO-GaAs heterojunction

Abstract

In this study, we analyze the reflectivity of a ZnO-GaAs heterojunction and how a depletion region may have an effect on the reflectivity of the material. We also tried to determine the thickness and effective refraction index of the thin film and intermediate layers using angular reflectivity. We performed a reflectivity experiment on three samples and compared the results to the simulations of the three models. Comparative analysis revealed that the four-layer model offered the best fit between the three models for the 10 mL, 15 mL and 20 mL. Based on the curve fitting we performed, the possible thickness of the thin film is d_{10 mL} = 172 nm, d_{15 mL} = 252 nm, and d_20mL = 206 nm. The non-uniform deposition of the ZnO film requires a model in which the refractive index differs from that of a uniformly deposited layer. Our analysis demonstrates that this conventional approach−which treats the depletion region as optically inactive−fails to match our experimental observations. This discrepancy highlights the need to consider the optical effects of the depletion region and study this topic in greater depth, with the goal of conducting a follow-up experiment that aims to electrically control the Goos-Hänchen shift using a heterojunction material.