Experimental Investigation of Si/SnOx Heterojunction for Its Tunable Optoelectronic Properties

We report growth and characterization of n-Si/p-SnO_x heterojunction using RF sputtering for deposition of p-type SnO_x under controlled growth oxygen pressure over n-type silicon (Si) wafer. The heterojunction properties of Si/SnO_x were varied by controlling the growth oxygen pressure of SnOx. Several characterization techniques, including PL (photoluminescence), AFM (atomic force microscopy), FESEM (field emission scanning electron microscopy), XRD, I-V characteristics and Hall measurement, were conducted to analyze the structural, optical, and electrical properties of the n-Si/p-SnOx heterojunction. The knee voltage (V_knee), or cut-in voltage, was calculated by analyzing the gradient of the dark current-voltage (J-V) curves when the bias was applied in the forward direction. The V_knee values for type-I, type-II, and type-III n-Si/p-SnO_x heterojunctions were determined to be 0.62 V, 0.84 V, and 1.0 V, respectively. The ideality factors (n₁ and n₂) were determined to be 1.52, 2.22, 3.52, and 8.41, 9.31, 10.34, respectively, for various heterojunction types. The reverse saturation current densities, J₀₁ and J₀₂ ranging from approximately 10⁻⁷ to 10⁻⁶ A/cm², and 10⁻⁵ to 10⁻⁴ A/cm², respectively. The objective of this experimental work is to investigate especially, the prospect of silicon /metal-oxide (Si/SnOx) based heterojunction to be used as optical sensors with tunable optoelectronic properties of SnOx.