High-Performance Graphene/AlGaN/GaN Schottky Junctions for Hot Electron Transistors

Abstract

The electronic properties of the graphene (Gr) Schottky junction with an Al0.22Ga0.78N/GaN heterostructure on silicon have been investigated, both by experiment and with use of ab initio DFT calculations. A peculiarly high n-type doping (1.1 × 1013 cm–2), observed for Gr in contact with AlGaN, was explained by the combined effect of Fermi level pinning by AlGaN surface states and charge transfer. Spatially uniform current injection across the Gr/AlGaN/GaN heterojunction was revealed by nanoscale resolution conductive atomic force microscopy (CAFM) analyses. Furthermore, a Gr/AlGaN/GaN Schottky diode with excellent rectifying behavior has been demonstrated and used as the key building block for a hot electron transistor (HET) with a 10 nm Al2O3 base-collector barrier. Thanks to the highly efficient hot electron injection from the AlGaN/GaN emitter, this transistor exhibits high on-state current density (J C,ON ≈ 1 A/cm2), high on-state over off-state current density ratio (J C,ON/J C,OFF ≈ 106), and a common-base current gain α ≈ 0.15, solely limited by the high Al2O3 base–collector barrier. The excellent performances of the Gr/AlGaN/GaN Schottky junction represent an important step toward the development of a HET technology compatible with the state-of-the-art GaN high electron mobility transistors.

Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures

“…In fact, this approach allows adding new functionalities to the existing semiconductor devices, and opening the way to the demonstration of new device concepts [Error! Bookmark not defined., 32,93]. In the last years, the integration of graphene and semiconducting TMDs with silicon and other semiconductors, such as GaN and related materials [94], has been explored by several research groups.…”

“…On the other hand, the integration of 2D materials with conventional bulk semiconductors can represent an easier root toward the exploitation of these low dimensional materials in (opto)electronics. In fact, this approach allows adding new functionalities to the existing semiconductor devices, and opening the way to the demonstration of new device concepts [11,32,93]. In the last years, the integration of graphene and semiconducting TMDs with silicon and other semiconductors, such as GaN and related materials [94], has been explored by several research groups.…”

There is plenty of room at the top: generation of hot charge carriers and their applications in perovskite and other semiconductor-based optoelectronic devices

“…The typical device architecture consists of three terminals (emitter, base, and collector) and, under a base-to-emitter polarization condition, the hot electrons are injected from the emitter to the base region. If the base thickness is shorter than the mean free path, the hot electrons can transit through the base region without any energy loss (ballistic transport) 121 , 122 . These THz transistors rely on a channel material that can accommodate high carrier densities suitable for low-contact resistance 123 , 124 .…”

Atomic Layer Deposition of High-k Insulators on Epitaxial Graphene: A Review

“…To date most of the studies on graphene growth have been carried out on the Si terminated (0001) face [40][41][42][43] and on the C terminated (000-1) face [40][41][42][43], due to the availability of large area SiC substrates with these orientations. Some experiments on the non-polar faces and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) have been recently reported as well [44]. Graphene films with very different structural and electronic properties (defectivity, thickness homogeneity, doping and mobility) have been obtained on these different crystal orientations, as a result of the different surface reconstructions during thermal decomposition.…”

“…Deposition of uniform ultra-thin insulators (especially high-k dielectrics) on graphene is a key step for the fabrication of graphene-based electronic devices [6,[14][15][16][17]. In this context, the atomic layer deposition (ALD), owing to its sequential layer-by-layer growth mechanism [18], is the most suitable candidate to achieve a conformal growth with subnanometric control on the thickness.…”