Composition-dependent Photoconductivities in Indium Aluminium Nitride Nanorods Grown by Magnetron Sputter Epitaxy

Photoconduction (PC) properties were investigated for ternary indium aluminium nitride (InxAl1-xN) nanorods (NRs) with different indium composition (x) from 0.35 to 0.68, as grown by direct-current reactive magnetron sputter epitaxy. Cross-sectional scanning transmission electron microscopy (STEM) reveals single-crystal quality of the vertically aligned InxAl1-xN NRs. Single-rod photodetector devices with good ohmic contacts were fabricated using the focused-ion-beam technique (FIB), where In-rich In0.68Al0.32N NR exhibits the optimal photocurrent responsivity at 1400 A/W and photoconductive gain at 3300. A transition from positive photoresponse to negative photoresponse was observed, while increasing the In composition x from 0.35 to 0.57. The negative PC was further enhanced by increasing x to 0.68. A model based on the coexistence and competition of deep electron trap states and recombination centers was proposed to explain the interesting composition-dependent PC in these ternary III-nitride 1D nanostructures.