Self-Powered GaN-Based MSM Ultraviolet Photodetector With Asymmetrical Interdigitated Structure

In this work, we propose a self-powered GaN-based high-performance metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) with an asymmetrical interdigitated structure. Benefiting from the device’s asymmetrically distributed energy band characteristics between the two electrodes, the peak responsivity ( <tex-math notation="LaTeX">R </tex-math> ) of 0.024 A/W under UV illumination corresponding to a high detectivity ( <tex-math notation="LaTeX">D^ </tex-math> ) of <tex-math notation="LaTeX">6.6×1012 </tex-math> cm <tex-math notation="LaTeX">· W⁻¹\,\,· </tex-math> Hz1/2 (Jones) can be obtained when the device is biased at 0 V. The results show that the self-powered function of the device can be achieved by using an asymmetric interdigitated structure. We illustrate the origin of the fabricated device’s photoresponse in the absence of bias with the assistance of energy band structure analysis, which can be attributed to the energy band bending caused by the polarization effect in AlGaN/GaN heterojunction. In addition, a high peak responsivity of 115 A/W and a photocurrent ( <tex-math notation="LaTeX">I_photo </tex-math> ) of <tex-math notation="LaTeX">2.66× 10⁻⁵ </tex-math> A at an applied bias voltage of 10 V was achieved. A dark current ( <tex-math notation="LaTeX">I_dark </tex-math> ) of <tex-math notation="LaTeX">1.18× 10⁻¹⁰ </tex-math> A was also measured, giving the device a photocurrent-dark current ratio ( <tex-math notation="LaTeX">I_photo / I_dark </tex-math> ) of 105. In short, the results show that the proposed self-powered GaN-based UV PD has the potential for high-sensitivity UV detection.