Extremely high-performing heterojunction device by surficial length enhanced effect

High-performing heterojunction devices were achieved by bringing an aluminum-doped ZnO (AZO) into contact with a p-Si substrate. A thin transparent AZO film was directly coated on pillar-array patterned Si and spontaneously formed a rectifying junction without any intentional doping process. Si pillar-arrays were designed to have 5 μm width with variation in periods (7 μm and 10 μm) used to modulate the surficial lengths. The light response is directly proportional to the surficial length enhancement. AZO/Si heterojunction devices showed strong dependence on the incident wavelengths. At a wavelength of 600 nm, the highest response ratio of 70,900% was achieved. We found that the locational superposition of the space charge region and the photo-generated region is crucial for light-reactive responses. We suggest an efficient geometric design scheme for highly efficient light-absorbers.