Hetero-integration of quasi two-dimensional PbZr_0.2Ti_0.8O₃ on AlGaN/GaN HEMT and non-volatile modulation of two-dimensional electron gas

In theory, two-dimensional electron gas (2DEG) density in AlGaN/GaN heterostructures can be modulated via the polarization of a ferroelectric material. Therefore, the integration of ferroelectric materials with AlGaN/GaN high electron mobility transistors (HEMTs) is a very attractive method for exploring further applications of electronic devices. This paper reports on the integration of single crystal PbZr_0.2Ti_0.8O₃ (PZT) thin films (20 nm) and AlGaN/GaN HEMT via a substrate transfer technique. Continuous and nonvolatile modulation of 2DEG density in the AlGaN/GaN heterojunction interface is achieved in accordance with the theory. By poling the PZT/AlGaN/GaN HEMT from 2 V to 7 V, the device exhibits different threshold voltages (from -3 V to 1 V). A modulation of 2DEG density up to 300% is achieved. Moreover, the retention characteristic of the device is excellent, and the variation of the threshold voltage is less than 0.25 V after 10⁵ s. Compared to the conventional method of depositing PZT directly on AlGaN/GaN HEMT, the transfer technique can achieve better quality in a much thinner film and prevent the interdiffusion during growth. At the same time, the excellent quality of the transferred PZT film has a good ability to modulate the 2DEG. The generality of our approach paves the way for integrating ferroelectric materials on the GaN-based devices, and this is promising for using the device in more application fields.