Low-to-mid Al content ($x\sim$ 0-0.56) Al$_x$In$_{1-x}$N layers deposited on Si(100) by radio-frequency sputtering

Abstract

Radio-frequency (RF) sputtering is a low-cost technique for the deposition of large-area single-phase AlInN on silicon layers with application in photovoltaic devices. Here, the effect of the Al mole fraction x from 0 to 0.56 on the structural, morphological, electrical, and optical properties of $n$ Al$_x$In$_{1-x}$N layers deposited at 550 $^\circ$C on p-Si(100) by RF sputtering is studied. X-ray diffraction data show a wurtzite structure oriented along the c-axis in all samples, where the full width at half maximum of the rocking curve around the InN (0002) diffraction peak decreases from $\sim 9^\circ$ to $\sim 3^\circ$ while incorporating Al to the AlInN layer. The rootmean-square surface roughness, estimated from atomic force microscopy, evolves from 20 nm for InN to 1.5 nm for Al$_{0.56}$In$_{0.44}$N. Low-temperature photoluminescence spectra show a blueshift of the emission energy from 1.59 eV (779 nm) for InN to 1.82 eV (681 nm) for Al$_{0.35}$In$_{0.65}$N according to the Al content rise. Hall effect measurements of Al$_x$In$_{1-x}$N ($0<x <0.35$) on sapphire samples grown simultaneously point to a residual n-type carrier concentration in the 1021 cm$^{-3}$ range. The developed n-AlInN/p-Si junctions present promising material properties to explore their performance operating as solar cell devices.