Quality improvement of AlInN/p-Si heterojunctions with AlN buffer layer deposited by RF-sputtering

The effect of an AlN buffer layer thickness on the structural, morphological and optical properties of n- Al0.37In0.63N deposited on p-Si (111) by radio-frequency sputtering was studied. The AlN/Al0.37In0.63N samples were structurally characterized via X-ray diffraction and high-resolution transmission electron microscopy showing that all layers present wurtzite structure highly oriented along the c-axis with no phase separation. All the samples present compact morphology with root-mean-square surface roughness below 1.7 nm and low-temperature photoluminescence emission centered at 1.8 eV. The presence of the buffer layer leads to an improvement of the structural quality, evidenced by a reduction of the full width at half maximum of the rocking curve around the (0002) Al0.37In0.63N reflection from 8° to 5°. Selected samples were processed and tested as solar cells showing a good rectifying behavior in the dark and an open circuit voltage of 0.35 V, a short circuit current density of 22.2 mA/cm2 and fill factor of 20% under 1 sun AM1.5G illumination.