Formation of wide band-gap CuInAlS2 thin film and its application to UV Detectors

• Wide bandgap CuIn0.09Al0.91S2 (3.27eV) film was formed by sulfurization of Cu/In/Al precursors at 700 °C for 100 min.
• The first UV photodetector using wide bandgap CuInAlS2 film has been demonstrated.
• More than one order of magnitude in photocurrent amplification can be achieved with 5-μm MSM structure.
• Spectral response of the photodetector is 0.72 A/W with cut off wavelength of 380 nm.
• The suggested bandgap of the CuIn0.09Al0.91S2 film is 3.27 eV.

An alternative route to form a wide band-gap Cu(In,Al)S2 (CIAS) thin film with Al content of approximately 23 at.% and its application to ultraviolet (UV) photodetectors (PDs) have been demonstrated. X-ray diffraction patterns and scanning electron microscope micrographs show that the CIAS thin film, formed by 700 °C sulfurization of Cu9Al4 (330) compound, is a single phased polycrystalline film with the (112)-preferred orientation and grain size of approximately 400–500 nm. At a 3 V bias voltage, the metal–semiconductor–metal structured UV PD has a dark current of 4.31 × 10− 9 A and a photocurrent of 6.55 × 10− 8 A using electrodes with 5-μm finger spacing. More than one order of magnitude in photocurrent amplification has been demonstrated. The spectral response of the PD is 0.72 A/W and the cut off wavelength occurs at 380 nm, which suggests that the band-gap of the CIAS film is 3.27 eV. The wide band-gap CIAS film has the potential to be a good candidate for UV PD applications.