MgZnO/ZnO Two-Dimensional Electron Gas Photodetectors Fabricated by Radio Frequency Sputtering

MgZnO/ZnO two-dimensional electron gas (2DEG) structures with ZnO annealed at various temperatures (600–900 °C) and photodetectors (PDs) with and without a 2DEG structure were fabricated using a radio frequency magnetron sputtering system. It was found that the carrier concentration and mobility increase with the annealing temperature owing to the improved crystalline in ZnO; however, high-temperature (800 °C or higher) annealing can degrade the crystalline of the ZnO layer. Hall measurements showed that compared with that of bulk ZnO, the sheet carrier concentration of the 2DEG sample increased from 1.3 × 1013 to 1.2 × 1014 cm–2, and the mobility was enhanced from 5.1 to 17.5 cm2/V s. This is because the channel layer is the total thickness (300 nm) in bulk ZnO, whereas the carriers are confined to a 45 nm region beneath the MgZO layer in the 2DEG sample, confirming the 2DEG behavior at the MgZnO/ZnO interface. The PDs with 2DEG structures demonstrate a higher ultraviolet (UV) response and a UV/visible r...