GaN-Based Trench Gate Metal Oxide Semiconductor Field Effect Transistors with Over 100 cm²/(V s) Channel Mobility

Abstract

Enhancement-mode metal oxide semiconductor field effect transistors (MOSFETs) with trench gate structures have been developed. These MOSFETs show excellent DC characteristics with on-voltage of 5.1 V, i.e., enhancement-mode operation and extremely high channel mobilities of 133 cm 2 /(V s). This structure enables us to realize vertical switching devices with high breakdown voltage and highly integrated low on-resistance with the usage of excellent physical parameters of GaN. This excellent performance of these devices breaks though the realization of GaN-based power switching transistors.

GaN-on-Si Quasi-Vertical Power MOSFETs

“…The channel mobility (µch) extracted using the equation from Ref. [8] in the liner region was 17.8 cm 2 /(V•s), which is comparable to the value in Ref.…”

“…[8] and [9] (this value is underestimated due to additional series resistance induced by the thick drift layer (4 μm) [32]). The lower µch is likely due to the typically larger defect density of GaN on silicon compared to that on bulk GaN substrates.…”

“…In addition, vertical MOSFETs can display normally-off operation, which is an important feature for power switching applications [5]- [7]. Rapid progress has been reported for high-performance vertical GaN transistors grown on n-type GaN substrates [8]- [20], mainly attributed to the capability of growing thick drift layers and the flexibility to form electrodes on the top and bottom of the devices. However, the high cost and availability of only small-size bulk GaN substrates limit their use for mass production.…”

“…To the best of our knowledge, this is the highest electron mobility in vertical GaN on Si. The fabricated vertical trench MOSFETs exhibited E-mode operation with a threshold voltage (Vth) of 6.3 V and an on/off ratio of over 10 8 . A specific on-resistance of 6.8 mΩ•cm 2 and a high off-state breakdown voltage of 645 V were achieved.…”

Quadrupole SIMS Analysis of Si Concentration in GaN Layers by a Molecular Ion Detection with a Minor Isotope

“…Recently, gallium nitride (GaN) -based metal-oxide-semiconductor field-effect transistors (MOSFETs) have begun to be studied and developed for the application to fail-safe high-power switching devices [1][2][3][4][5][6]. Donor doping with Si is the most common method for achieving n-type conducting GaN.…”