Researchers from the University of Granada, led by Dr. Francisco B. Naranjo, have published a study in the Journal of Applied Physics exploring the properties of AlInN layers deposited on silicon substrates using a cost-effective technique. The team investigated how varying the aluminum content in these layers affects their structural, morphological, electrical, and optical properties, with an eye towards potential applications in photovoltaic devices.
The researchers employed radio-frequency (RF) sputtering, a low-cost method suitable for large-area deposition, to create AlInN layers on silicon substrates. They found that increasing the aluminum content in the layers, from 0 to 56%, resulted in significant changes in the material’s properties. X-ray diffraction analysis revealed that all samples exhibited a wurtzite crystal structure oriented along the c-axis. Notably, the crystal quality improved with higher aluminum content, as evidenced by a decrease in the full width at half maximum of the rocking curve around the InN (0002) diffraction peak.
The surface roughness of the layers also decreased with increasing aluminum content, dropping from 20 nm for pure InN to just 1.5 nm for Al0.56In0.44N. This improvement in surface morphology is beneficial for photovoltaic applications, as smoother surfaces can lead to better device performance. Low-temperature photoluminescence measurements showed a blueshift in the emission energy as the aluminum content increased, with the emission energy rising from 1.59 eV for InN to 1.82 eV for Al0.35In0.65N. This shift in emission energy is a result of the bandgap widening that occurs with increasing aluminum content.
Hall effect measurements of AlInN layers grown simultaneously on sapphire substrates indicated a residual n-type carrier concentration in the range of 10^21 cm^-3 for aluminum contents below 35%. The researchers also demonstrated that the developed n-AlInN/p-Si junctions exhibit promising material properties for potential use in solar cell devices. The study highlights the potential of RF sputtering for depositing large-area AlInN layers on silicon substrates, offering a cost-effective route for the development of next-generation photovoltaic devices.
Source: R. Blasco, S. Valdueza-Felip, D. Montero, M. Sun, J. Olea, and F. B. Naranjo, “Low-to-mid Al content (x∼ 0-0.56) AlxIn1−xN layers deposited on Si(100) by radio-frequency sputtering,” Journal of Applied Physics (2023).
This article is based on research available at arXiv.