Photoelectrochemically recessed AlGaN/GaN monolithic inverter incorporating LiNbO3 ferroelectric film

In this work, the AlGaN/GaN monolithic inverters were integrated by the enhancement-mode metal-oxide-semiconductor high-electron-mobility transistors (E-mode MOSHEMTs) and the depletion-mode metal-oxide-semiconductor high-electron-mobility transistors (D-mode MOSHEMTs). For the fabrication of the E-mode MOSHEMTs, the LiNbO₃ (LNO) ferroelectric films deposited on the photoelectrochemically (PEC)-recessed structure effectively compensated the two dimensional electron gas (2DEG) channel existed in the AlGaN/GaN heterostructure. For the fabrication of the D-mode MOSHEMTs, the PEC wet etching method and the surface treatment were utilized to form the various-thick etched AlGaN layers with low surface defects. Therefore, the operating current of the D-mode MOSHEMTs could be controlled. Finally, the resulting monolithic inverters with a suitable current ratio (β) of 25 were successfully fabricated. The corresponded output swing (between VOH-VOL), the noise margin high (NMH: VOH-VIH), and the noise margin low (NML: VIL-VOL) were respectively about 4.9 V, 1.9 V, and 1.7 V, when the input signal was 5 Vp-p. Most importantly, the corresponded output voltage (Vout) was 2.5 V which equaled to the half of VDD according to the voltage transfer characteristics (VTC) of the resulting inverters, when the input voltage (VIN) was 2.5 V. It indicated that the monolithic inverters have an unskewed inverter property.