Role of the i-layer thickness in the performance of a-Si: H Schottky barrier photodiodes

In this work we present the current/voltage characteristics of Si:H/Pd Schottky structures using high quality, low defect density amorphous silicon (a-Si:H) deposited by a non-conventional, modified triode PECVD method. This new configuration allows the deposition of compact and high quality a-Si:H with a photosensitivity of 10⁷, yielding films with low bulk defects. AFM measurements also revealed that these films have a very smooth surface allowing a low defect interface between the metal and the a-Si:H. As a result, we show that by using these a-Si:H films and by proper control of the i-layer thickness the reverse dark current of the diode can be highly reduced achieving signal to noise ratio of 10⁶, surpassing the results usually achieved by p-i-n structures.