Low-to-mid Al content (x~0-0.56) AlxIn1-xN layers deposited on Si(100) by RF sputtering

Abstract

Radio frequency sputtering is a low-cost technique for the deposition of large-area single-phase AlInN on silicon layers with application in photovoltaic devices. Here we study the effect of the Al mole fraction x from 0 to 0.56 on the structural, morphological, electrical and optical properties of n-AlxIn1-xN layers deposited at 550ºC on p-Si(100) by radio frequency sputtering. 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 ~9º to ~3º when incorporating Al to the AlInN layer. The root mean square surface roughness, estimated from atomic force microscopy, evolves from 20 nm for InN to 1.5 nm for Al0.56In0.44N. Low-temperature photoluminescence spectra show a blue shift of the emission energy from 1.59 eV (779 nm) for InN to 1.82 eV (681 nm) for Al0.35In0.65N accordingly to the Al content rise. Hall effect measurements of AlxIn1-xN (0 < x < 0.35) on sapphire samples grown simultaneously point a residual n-type carrier concentration in the 1021 cm-3 range. The developed n-AlInN/p-Si junctions present optimal material properties to explore their performance operating as solar cell devices.