High-efficiency and low dark current crystalline selenium-based heterojunction photodiode with a high-quality tellurium nucleation layer
In this study, a high-efficiency and low dark current thin-film crystalline selenium (c-Se)/gallium oxide (Ga2O3) heterojunction photodiode is demonstrated via improving the deposition conditions for the tellurium nucleation layer that prevents the peeling of the selenium film during annealing. The highly (100)-oriented polycrystalline selenium film is grown by employing a thin tellurium (Te) nucleation layer with high-quality crystallinity. The device exhibits high external quantum efficiency in the visible region and extremely low dark current that is below 100 pA/cm2 at a reverse-bias voltage of 15 V at room temperature. The result indicates the high potential of crystalline selenium-based photodiodes to be used as photoconversion layers in imaging devices.
Rectification phenomena and photovoltaic effects in an amorphous Se1−x1Tex1‐Se1−x2Tex2 heterostructure
A heterostructure of amorphous Se1−x1Tex1‐Se1−x2Tex2 was investigated. A photovoltage characteristic and rectification characteristics were detected in the structure. To investigate the mechanism, the spectral dependence of the photoconductivity, the photovoltaic effect, and the thermoelectric power were measured. It was found that the characteristics of the heterostructure could be explained by the model of a p+p junction.
Lucky drift impact ionization in amorphous semiconductors
The review of avalanche multiplication experiments clearly confirms the existence of the impact ionization effect in this class of semiconductors. The semilogarithmic plot of the impact ionization coefficient (α) versus the reciprocal field (1∕F) for holes in a-Se and electrons in a-Se and a-Si:H places the avalanche multiplication phenomena in amorphous semiconductors at much higher fields than those typically reported for crystalline semiconductors with comparable bandgaps. Furthermore, in contrast to well established concepts for crystalline semiconductors, the impact ionization coefficient in a-Se increases with increasing temperature. The McKenzie and Burt [S. McKenzie and M. G. Burt, J. Phys. C 19, 1959 (1986)] version of Ridley’s lucky drift (LD) model [B. K. Ridley, J. Phys. C 16, 3373 (1988)] has been applied to impact ionization coefficient versus field data for holes and electrons in a-Se and electrons in a-Si:H. We have extracted the electron impact ionization coefficient versus field (αe vs F...