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.

In this brief, a scaled In $_{{0}.{17}}$ Al $_{{0}.{83}}\text{N}$ /GaN high-electron-mobility transistor (HEMT) was fabricated on sapphire substrate with 47-nm ${T}$ -gate length, 300-nm source–drain distance, and selective area regrown $\text{n}^{+}$ -GaN. The device exhibits cutoff frequencies ${f}_{\text {T}}/{f}_{\text {max}}$ of 190/301 GHz, which gives a record sqrt ( ${f}_{\text {T}} \times {f}_{\text {max}}{)}$ = 239 GHz among reported Ga-polar GaN-on-sapphire HEMTs. The device shows a maximum current density, a peak external direct current transconductance, and an ${I}_{\text {on}}/{I}_{\text {off}}$ ratio of 1.45 A/mm, 610 mS/mm, and $2.9\times 10^{6}$ , respectively. Drain-induced barrier lowering of 75 mV/V is measured at ${I}_{\text {ds}}$ = 1 mA/mm between ${V}_{\text {ds}}$ = 1 V and 5 V. The three-terminal OFF-state breakdown voltage is 14.7 V. The effective electron velocity of the 2-D electron gas (2DEG) under the gate foot is estimated to be $1.4\times 10^{7}$ cm/s. These characteristics of this Ga-polar millimeter wave (mm-wave) GaN-on-sapphire HEMT are comparable with those state-of-the-art counterparts on SiC substrates.

A surface acoustic wave (SAW) resonator with quality factors ( Q ) of 3526/10205 at the resonant/anti-resonant frequencies ( f _r / f _a ) has been fabricated on thick MOCVD grown (0002) AlN films (4 μ m) on Sapphire. The impact of device parameters on Q of resonators, including aspect ratio of length to width ( L/W ), number of interdigital transducers, and IDT metal thickness, has been investigated. The high Q is obtained due to the large L/W value of 12 which can enhance the acoustic energy superimposition of interdigital transducers, and the thick AlN film (4 μ m), which can reduce the negative impact of seed layer. Moreover, temperature coefficient of frequency (TCF) values of -46.52/-46.09 ppm/°C for f _r / f _a with temperatures ranging from -50 °C to 250 °C and a high Q of 4027 at 250 °C of the resonator have been demonstrated for temperature sensor application.