Optimizing SiGe–SiO2 Visible–Short‐Wave Infrared Photoresponse by Modulating Interplay Between Strain and Defects Through Annealing

Abstract

SiGe‐SiO2‐based structures present high interest for their high photosensitivity from visible to short‐wavelength infrared. Herein, two postdeposition annealing procedures, that is, rapid thermal annealing (RTA) and rapid‐like furnace annealing (FA), are compared. Both RTA and FA are performed at 600 °C for 1 min for SiGe nanocrystals (NCs) formation in SiO2 matrix in Si/SiO2/SiGe/SiO2 structures deposited by magnetron sputtering. The FA imitates RTA resulting in enhanced spectral response. X‐ray diffraction, transmission electron microscopy, and Raman spectroscopy are carried out showing Ge‐rich SiGe NCs with 11.3 ± 1.2 nm size for RTA and 9.4 ± 0.8 nm for FA. Photocurrent spectra for both structures show several peaks that are annealing dependent. The photocurrent intensity for FA samples is ≈7 times higher than RTA samples while cutoff wavelengths are slightly different, that is, 1365 nm for FA and 1375 nm for RTA. The FA structures show (at −1.5 V) over 4 A W−1 responsivity at 730 nm, 6.4 × 107 Jones detectivity at 735 nm, and 2.2 × 107 Jones at about 1210 nm. FA structures contain small SiGe NCs with incorporated residual strain, while RTA ones are formed of columnar SiGe NCs separated by SiGeOx amorphous regions and show increased tensile strain in the SiGe.