Dependence of photocurrent on UV wavelength in ZnO/Pt bottom-contact Schottky diode

• The bottom-contacted Schottky diode is devised by growing (000l) ZnO on (111) Pt.
• The photo-response strongly depends on the wavelength of ultra-violet (UV) light.
• Photo-current is considerably increased when illuminating longer-wavelength-UV.
• The behavior results from the wavelength-dependent penetration depth of UV in ZnO.

We fabricated the bottom-contacted ZnO/Pt Schottky diode and investigated the dependence of its photocurrent on the wavelength of illuminated ultraviolet (UV) light source. The bottom-contacted Schottky diode was devised by growing (000l) ZnO on (111) Pt, and the fabricated device showed a strong dependence on the UV wavelength for its photo-response characteristics. When longer-wavelength-UV (e.g., UV-A) was illuminated on the device, the photo-current was increased by a factor of 200, compared to that under illumination of shorter-wavelength-UV (e.g., UV-C). The behavior is attributed to the wavelength-dependent UV penetration depth for ZnO.