Bias-voltage dependent ultraviolet photodetectors prepared by GaOx + ZnO mixture phase nanocrystalline thin films

• GaOx + ZnO thin films sputtered and annealed exhibit interesting and unique optical properties, especially deep UV photo response.
• GaOx + ZnO thin films can be used to fabricate efficient deep UV photodetectors.
• The mixture phase nature of GaOx + ZnO thin films is revealed to be responsible for the unique characteristics of the photodetectors.
• Two bands in UV range can be adjusted by a applied voltage when the PDs were fabricated using the mixture phase nature of GaOx + ZnO thin films.

Ultraviolet (UV) photodetectors were prepared by using the GaOx + ZnO mixture phase thin films sputtered on sapphire as the photoresponse layer. The devices show good photoresponse in UV range. More interestingly, the device responsivity in the wavelength less than 280 nm range rapidly increases with increasing the applied voltage and becomes dominant for the bias ⩾3.0 V. X-ray diffraction, absorption and cathodoluminescence measurements firmly reveal the mixture phases in the thin films. Electric field dependent detrapping of photo-excited carriers in nanocrystals in the films shall be responsible for the observed bias-voltage dependent deep UV photoresponse of the devices.