The past decades have witnessed a tremendous development of GaN-based power electronic devices grown on Si substrate. This article provides a concise introduction, review, and outlook of the research developments of GaN-on-Si power device technology. The comprehensive review has discussed the crucial issues in the state-of-the-art device technology based on both GaN materials epitaxy including stress control and point defects study, and device fabrication including normally off solutions like Cascode, trench MIS-gate, and p-GaN gate. Device reliability and other common fabrication issues in GaN high electron mobility transistors (HEMTs) are also discussed. Lastly, we give an outlook on the GaN-on-Si power devices from two aspects, namely high frequency, and high power GaN ICs, and GaN vertical power devices.

A large lattice-mismatch induced stress control technology with a low Al content AlGaN layer has been used to grow high quality GaN layers on 4-in. Si substrates. The use of this technology allows for high mobility AlGaN/GaN heterostructures with electron mobility of 2040 cm²/(V·s) at sheet charge density of 8.4 × 10¹²cm⁻². Strain relaxation and dislocation evolution mechanisms have been investigated. It is demonstrated that the large lattice mismatch between the low Al content AlGaN layer and AlN buffer layer could effectively promote the edge dislocation inclination with relatively large bend angles and therefore significantly reduce the dislocation density in the GaN epilayer. Our results show a great potential for fabrication of low-cost and high performance GaN-on-Si power devices.

Carbon (C) doping is essential for producing semi-insulating GaN for power electronics. However, to date the nature of C doped GaN, especially the lattice site occupation, is not yet well understood. In this work, we clarify the lattice site of C in GaN using polarized Fourier-transform infrared and Raman spectroscopies, in combination with first-principles calculations. Two local vibrational modes (LVMs) at 766 and $774{\mathrm{cm}}^{-1}$ in C doped GaN are observed. The $766{\mathrm{cm}}^{-1}$ mode is assigned to the nondegenerate $A_1$ mode vibrating along the $\mathit{c}$ axis, whereas the $774{\mathrm{cm}}^{-1}$ mode is ascribed to the doubly degenerate $E$ mode confined in the plane perpendicular to the $\mathit{c}$ axis. The two LVMs are identified to originate from isolated ${\mathrm{C}}_{\mathrm{N}}^{-}$ with local $C_{3v}$ symmetry. Experimental data and calculations are in outstanding agreement both for the positions and the intensity ratios of the LVMs. We thus provide unambiguous evidence of the substitutional C atoms occupying the N site with a $-1$ charge state in GaN and therefore bring essential information to a long-standing controversy.

High quality Al₂O₃ film grown by atomic layer deposition (ALD), with ozone (O₃) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al–O–H and Al–Al bonds in ALD-Al₂O₃ has been realized by substituting conventional H₂O source with O₃. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O₃-Al₂O₃ and 2-nm H₂O-Al₂O₃ interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 10¹²cm⁻², contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance R_ON,sp of 0.49 mΩ cm².