Structural, Electrical and Photovoltaic Characteristics of n-ZnSe/ p-GaAs Heterojunction

Heterojunction of n-ZnSe/p-GaAs devices were fabricated by growing n-ZnSe films onto p-type GaAs using flash evaporation technique. The elemental composition of the prepared films was confirmed by energy dispersive X-ray (EDX) spectroscopy. The morphology and crystal structure of the film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The dark current–voltage (I–V) measurements were performed in the temperature range 300 to 400 K. The measured electrical parameters were used to determine the conduction mechanisms of this heterojunction. The forward current was found to be increased exponentially with the applied voltage in the region of V ≤ 0.3 V, which was dominated by the thermionic emission over the n-ZnSe/p-GaAs interface. In the region 0.4 < V ≤ 1 V, the current transport was due to the space-charge-limited current controlled by single trap level of 0.29 eV. A free carrier concentration and built-in potential were estimated from the dark capacitance–voltage measurements at 1 MHz. The current-voltage characteristics were also studied for n-ZnSe/p-GaAs heterojunction under illumination and the photovoltaic parameters were evaluated.