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Gate dielectrics for gallium nitride (GaN) high electron mobility transistor (HEMT) technology have always been challenging because of the nonideal semiconductor–dielectric interface, which leads to electronic traps. Plasma‐enhanced chemical vapor deposition and atomic layer deposition are standard techniques, but they require surface treatment and post‐annealing to control these traps. This article explores metal organic chemical vapor deposition‐grown in situ aluminum nitride (AlN) as a gate dielectric. The interface is expected to be pristine as there is no change in the chamber environment. A thin (10 nm) AlN layer is deposited at a low temperature to minimize strain and prevent the formation of an unwanted conductive channel within the device. The electrical and structural properties of this AlN‐capped HEMT are compared to a standard GaN‐capped HEMT, including temperature‐dependent studies. The results show that the AlN‐capped HEMT retains a higher charge in the channel while having an order of magnitude lower gate leakage than the GaN‐capped sample. Furthermore, the AlN‐capped HEMT performs similarly to the GaN‐capped HEMT in terms of temperature‐dependent leakage, dynamic on‐resistance, and temperature coefficient of resistance. [ABSTRACT FROM AUTHOR]

Large‐area, complementary metal–oxide semiconductor‐compatible substrates for high‐performance graphene‐based electronic devices are desired and AlN is a promising candidate with high dielectric constant and low surface phonon densities. An informed choice of substrate needs to consider the simultaneous effects of the two major substrate‐induced scattering mechanisms—remote impurity scattering and remote interfacial phonon scattering. Herein, the effects of such an interplay with fundamentally different electron and hole transport characteristics in chemical vapor deposition (CVD)‐grown monolayer graphene field‐effect transistors (FETs) on AlN thin films are demonstrated, due to the polar and piezoelectric nature of AlN. Temperature‐dependent measurements not only reveal a cross‐over in mobility, with graphene FETs on AlN having larger mobilities than SiO2 at higher temperatures, but also an asymmetry between the cross‐over temperature for the electron and hole branches. Theoretical transport model using appropriate densities of charged impurities in both cases is shown to match well with the experimental results. These results highlight the role of the actual charge configurations within thin‐film dielectric substrates on carrier transport in practically realizable graphene FETs, which can be further generalized to other 2D material systems. [ABSTRACT FROM AUTHOR]

A negative‐capacitance high electron mobility transistor (NC‐HEMT) with low hysteresis in the subthreshold region is demonstrated in the wide bandgap AlGaN/GaN material system using sputtered BaTiO3 as a "weak" ferroelectric gate in conjunction with a conventional SiNx dielectric. An enhancement in the capacitance for BaTiO3/SiNx gate stacks is observed in comparison to control structures with SiNx gate dielectrics directly indicating the negative capacitance contribution of the ferroelectric BaTiO3 layer. A significant reduction in the minimum subthreshold slope for the NC‐HEMTs is obtained in contrast to standard metal‐insulator‐semiconductor HEMTs with SiNx gate dielectrics—97.1 mV dec−1 versus 145.6 mV dec−1—with almost no hysteresis in the ID–VG transfer curves. These results are promising for the integration of ferroelectric perovskite oxides with III‐Nitride devices toward NC‐field‐effect transistor switches with reduced power consumption. [ABSTRACT FROM AUTHOR]

The ultrathin channel in 2D semiconductors, although playing host to several interesting properties, also renders strong interactions (scattering) of charge carriers with the surrounding medium. The over‐arching dominance of surface (interfacial) optical phonons in 2D charge transport and engineering ideal nitride‐based dielectric environments for large performance gains is reported. Charge transport in MoS2 field effect transistors (FETs) fabricated on three conventional substrates, SiO2, Al2O3, and HfO2, is contrasted with a newly introduced, CMOS‐compatible nitride‐based dielectric: aluminum nitride (AlN) by employing semi‐classical models which account for charged impurity, surface optical phonon, and intrinsic phonon scattering. Unlike previous reports focused on charge impurity scattering, this work presents a new paradigm of utilizing high optical phonon energies intrinsic to “stiff” nitride bonds. This results in substantially lower surface optical phonon scattering in 2D FETs which directly influences peak field effect (FE) mobility, high field mobility degradation, and temperature‐dependent mobility. Leveraging on these insights, high‐performance sulfur‐passivated MoS2 FETs with an optimum all‐nitride environment (hexagonal boron nitride/MoS2/AlN) are demonstrated with FE mobility up to 72.8 cm2 V−1 s−1. This work is envisioned to address important issues in design of dielectric environments for a host of applications based on 2D materials. [ABSTRACT FROM AUTHOR]