The influence of hydrogen passivation of silicon on the photocurrent of CdS/Si heterodiodes

A CdS/p-Si:H heterojunction is formed by the evaporation of CdS on a hydrogen passivated Si wafer. It is found that the substrate passivation procedure has a strong influence on the photocurrent properties of the CdS/p-Si interface. In fact, in addition to the photoresponse in the red and infrared spectral ranges, the CdS/p-Si:H heterodiode also reveals photocurrent in the blue and green. This is in contrast to CdS/p-Si and CdS/p-InP devices, which do not exhibit photocurrent in the absorption region of CdS. The positive influence of the passivation on the optoelectronic properties of the CdS/p-Si:H heterodiode is explained by the prevention of interface reactions during the formation of the device. The dependence of the photocurrent of the CdS/p-Si:H heterodiode on an applied bias gives evidence of a homojunction-like behavior.