MgZnO MSM UV Photodetector with Different Annealing Temperatures by RF Magnetron Sputtering

Abstract

We investigated the MgZnO metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) with different annealing temperatures grown by RF magnetron sputter. The MgZnO MSM PD at an annealing temperature of 700 °C has the lowest dark-current and the highest photo- to dark-current ratio (PDRC), which are 5.93 × 10−11 and 5.69 × 104 A at a bias voltage of −5 V, respectively. Higher annealing temperature improves the dark-current due to less grain boundary and number of oxygen vacancies (Ov). The PD without annealing process has the highest responsivity of 0.189 A W−1, and the external quantum efficiency (EQE) achieves to 63.3% due to the persistent photoconductivity (PPC) effect. However, a massive number of interface defects provide a leakage path for dark-current that reduces the responsivity ratio of ultraviolet to visible light (RUV peak/R440 nm). Conversely, the responsivity ratio of ultraviolet to visible light of MgZnO MSM PD annealed at 700 °C achieves to 9.83 due to high crystal quality. Finally, the device using MgZnO target material with 20% Mg content keeps a Mg content of 14.2% at an annealing temperature of 700 °C higher than the as-grown device (only Mg content of 6.2%).