Leakage current reduction in n-GaN/p-Si (100) heterojunction solar cells

We report on the growth of n-GaN/p-Si heterojunction solar cells via thermal chemical vapor deposition on Si (100) substrates at different growth temperatures (900, 950, and 1000 degrees C). The influence of growth temperature on the morphological, structural, optical, and electrical properties of GaN films has been elucidated. Increasing the growth temperature was found to reduce the internal stress and improve the material's crystallinity as confirmed via x-ray diffraction and Raman spectroscopy analyses. The photoluminescence spectra exhibit strong near band edge peaks in the range between 375 and 366nm, with the peak intensity increasing with increasing the growth temperature. The current-voltage (J-V) characteristics of the assembled heterojunction solar cells showed the reverse leakage current to decrease with increasing the growth temperature. Consequently, the solar cell fabricated using the films grown at 1000 degrees C exhibits higher conversion efficiency (8.17%) than those grown at 950 degrees C (5.15%) and 900 degrees C (2.48%), respectively. This work shows that the structural, optical, and photovoltaic properties of the grown n-GaN/p-Si heterojunction solar cell structures are strongly influenced by the growth temperature.