Peigang Li

Construction of GaN/Ga2O3 p–n junction for an extremely high responsivity self-powered UV photodetector

A self-powered ultraviolet photodetector was constructed with GaN/Ga2O3 p–n junction by depositing n-type Ga2O3 thin film on Al2O3 single crystals substrate covered by p-type GaN thin film. The fabricated device exhibits a typical rectification behavior in dark and excellent photovoltaic characteristics under 365 nm and 254 nm light illumination. The device shows an extremely high responsivity of 54.43 mA W−1, a fast decay time of 0.08 s, a high Ilight/Idark ratio of 152 and a high detectivity of 1.23 × 1011 cm Hz1/2 W−1 under 365 nm light with a light intensity of 1.7 mW cm−2 under zero bias. Such excellent performances under zero bias are attributed to the rapid separation of photogenerated electron–hole pairs driven by built-in electric field in the interface depletion region of GaN/Ga2O3 p–n junction. The results strongly suggest that the GaN/Ga2O3 p–n junction based photodetectors are suitable for applications in secure ultraviolet communication and space detection which require high responsivity and self-sufficient functionality.

Composition tuning of rectifying polarity of colloidal CdS1−xSex nanocrystal-based devices

CdS1–xSex colloidal nanocrystals (NCs) were synthesized by colloidal chemistry route. Both lattice parameters and band structure were modulated by tuning the content of Se. As the Se content increases, the peak of UV–Visible absorbance spectrum of CdS1−xSex shifts toward longer wavelength direction, indicating the reduction of band gap. Devices with Au/CdS1−xSex NCs/Au structures have been fabricated by assembling the obtained CdS1−xSex NCs into Au microelectrodes via dielectrophoresis method. It is found that the rectifying polarities of the devices are strongly dependent on the content of Se. With the increasing Se content, the rectification polarity changes from backward to forward. This polarity tuning could be caused by the change of the relative height of the Fermi levels between CdS1−xSex and Au. The Se-content-dependent rectifying behavior may offer us an opportunity to design novel logical structure in NC-based nanoelectronics.