Insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor devices with Al2O3 or AlTiO gate dielectrics

Abstract

We have investigated insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor (MIS) devices with Al2O3 or AlTiO (an alloy of Al2O3 and TiO2) gate dielectrics obtained by atomic layer deposition on AlGaN. Analyzing insulator-thickness dependences of threshold voltages for the MIS devices, we evaluated positive interface fixed charges, whose density at the AlTiO/AlGaN interface is significantly lower than that at the Al2O3/AlGaN interface. This and a higher dielectric constant of AlTiO lead to rather shallower threshold voltages for the AlTiO gate dielectric than for Al2O3. The lower interface fixed charge density also leads to the fact that the two-dimensional electron concentration is a decreasing function of the insulator thickness for AlTiO, whereas being an increasing function for Al2O3. Moreover, we discuss the relationship between the interface fixed charges and interface states. From the conductance method, it is shown that the interface state densities are very similar at the Al2O3/AlGaN and AlTiO/AlGaN interfaces. Therefore, we consider that the lower AlTiO/AlGaN interface fixed charge density is not owing to electrons trapped at deep interface states compensating the positive fixed charges and can be attributed to a lower density of oxygen-related interface donors.

Comparative Study of Characteristics and Interface States with and without Post‐Gate‐Annealing Treatment for AlGaN/GaN‐Recessed Metal–Insulator–Semiconductor High Electron Mobility Transistors Using HfO2 Gate Insulator on Si Substrates

“…The density of fixed charges is derived from the V th shift, which is based on the V th model for the MIS‐HEMT . The energy band and interfacial charge distribution are shown in Figure .…”

GaN-based MIS-HEMTs with Al2O3 dielectric deposited by low-cost and environmental-friendly mist-CVD technique

“…4) High quality Al 2 O 3 thin films are usually deposited using atomic layer deposition (ALD) and other deposition techniques under vacuum conditions. [5][6][7][8][9][10][11] It is reasonable to say that the ALD technique has paved the way for the manufacture of III-V MOSFETs, because it can provide high-grade oxides/III-V interfaces. 2) Meanwhile, mist chemical vapor deposition (mist-CVD) technique has been steadily growing in popularity as an ecofriendly alternative approach for depositing oxide films.…”

Analysis of inverse-piezoelectric-effect-induced lattice deformation in AlGaN/GaN high-electron-mobility transistors by time-resolved synchrotron radiation nanobeam X-ray diffraction

“…This indicates a sufficiently low charge density at the Al 2 O 3 /AlGaN interface, leading to a possibility that the negative polarization charge at the AlGaN surfaces is compensated by some charges originating from an AlGaN surface donor state, interface states and ionized donor states of the oxide layer located near the conduction band edge. [26][27][28][29][30] Thus, we carried out the calculation without assuming interface charges at Al 2 O 3 /AlGaN interface. Figure 3 shows the calculated energy-band diagrams for gate voltages of −7, 0, and +7 V. As shown in Fig.…”