Deep Ultraviolet C Phototransistors Using Aluminum-Doped Gallium Hafnium Oxide Channel Layer

In the work, a vapor cooling condensation system was utilized to deposit various aluminum-doped gallium hafnium oxide (AlHfGaO) films at approximately 80 K. The various AlHfGaO films were used as the channel layers of deep ultraviolet (UV) C phototransistors. The undesired oxygen vacancy defects residing in the AlHfGaO films could be compensated and suppressed by doping Al dopants. Even though the cutoff wavelength of the phototransistors could be modulated by doping various Al atomic contents in the AlHfGaO channel layers, the performances of the resulting phototransistors could be improved due to the reduction of the amount of oxygen vacancy defects. Compared with the phototransistors using the HfGaO channel layer, when the phototransistors using the AlHfGaO channel layer with an Al atomic content of 3.16%, its cutoff wavelength was shifted from 240 to 225 nm, and the detectivity was improved from 1.62 \times \,\,10^{{12}} to 3.16 \times \,\,10^{{12}} Jones. Besides, the photoresponse speed was also improved.