High quantum efficiency LEDs with InGaN/GaN/AlGaN/GaN MQWs have been demonstrated. The proposed GaN interlayer barrier can not only increase the concentration and the spatial overlap of carriers, but also improve the quality of the MQWs.
Conventional silicon (Si)-based power devices face physical limitations—such as switching speed and energy efficiency—which can make it difficult to meet the increasing demand for high-power, low-loss, and fast-switching-frequency power devices in power electronic converter systems. Gallium nitride (GaN) is an excellent candidate for next-generation power devices, capable of improving the conversion efficiency of power systems owing to its wide band gap, high mobility, and high electric breakdown field. Apart from their cost effectiveness, GaN-based power high-electron-mobility transistors (HEMTs) on Si substrates exhibit excellent properties—such as low ON-resistance and fast switching—and are used primarily in power electronic applications in the fields of consumer electronics, new energy vehicles, and rail transit, amongst others. During the past decade, GaN-on-Si power HEMTs have made major breakthroughs in the development of GaN-based materials and device fabrication. However, the fabrication of GaN-based HEMTs on Si substrates faces various problems—for example, large lattice and thermal mismatches, as well as ‘melt-back etching’ at high temperatures between GaN and Si, and buffer/surface trapping induced leakage current and current collapse. These problems can lead to difficulties in both material growth and device fabrication. In this review, we focused on the current status and progress of GaN-on-Si power HEMTs in terms of both materials and devices. For the materials, we discuss the epitaxial growth of both a complete multilayer HEMT structure, and each functional layer of a HEMT structure on a Si substrate. For the devices, breakthroughs in critical fabrication technology and the related performances of GaN-based power HEMTs are discussed, and the latest development in GaN-based HEMTs are summarised. Based on recent progress, we speculate on the prospects for further development of GaN-based power HEMTs on Si. This review provides a comprehensive understanding of GaN-based HEMTs on Si, aiming to highlight its development in the fields of microelectronics and integrated circuit technology.
GaN-based high electron mobility transistors (HEMTs) have exhibited great application prospects in power and radio frequency devices, thanks to the superior properties of GaN. Despite the significant commercialization progress, the reliability of GaN-based HEMTs remains a challenge. This work experimentally investigates the time-dependent degradation of Mg-doped GaN/AlN superlattice HEMTs under both OFF-state and SEMI-ON-state bias conditions and proposes that GaN/AlN superlattices as a barrier can solve the Vth instability issues of GaN HEMTs under OFF-state and SEMI-ON-state bias conditions. On the one hand, in the SEMI-ON-state, the hot electron effect leads to the degradation of Ig, gm,max, and Id,sat to varying degrees. However, the as-prepared GaN-based HEMTs exhibit excellent Vth stability (almost no change) under hot electron injection, on the account of the excellent two-dimensional electron gas confinement in the GaN/AlN superlattice structure. On the other hand, in the OFF-state, positive Vth shift (about 0.12 V) is induced by the hole emission in the GaN/AlN superlattice structure under reverse bias stress. In addition, the stress-induced destruction of MgO gate dielectric gives rise to the gate leakage, which increases by 2 orders of magnitude and triggers an irreversible degradation (about 10%) of the gm,max. These results are expected to provide a solution to the Vth instability of GaN HEMTs.
A novel E-mode GaN high-electron-mobility field-effect transistor with a superlattice barrier doped with Mg by thermal diffusion. This strategy can provide new ideas for the commercialisation of E-mode devices.
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