Frequency-dependent conductance measurements were carried out to investigate the trap states in Al 2 O 3 /AlInGaN/GaN metal-insulator-semiconductor (MIS) heterostructures. From the electrical measurements, an improvement in trap state characteristics was observed for the device fabricated with lower In composition in quaternary nitride layers. In the presence of higher In composition, segregation of In atoms was observed in AlInGaN layers. Because of this Insegregation, surface quality of the quaternary-N deteriorated that led to the formation of trap states at and near the oxide/semiconductor interface. Therefore, in the presence of lower In composition, an improvement in trap characteristics was observed for the AlInGaN/GaN-based MIS devices.

The authors are reporting for the first time the fabrication of GaN-based fully-vertical high-power metal-oxide-semiconductor field effect transistors on Si. The electrical measurements of the fabricated device exhibited both vertical and lateral modes of operation. The transfer characteristics of the device in vertical mode showed a peak trans-conductance (G m, max) of 23.6 mS/mm with a threshold voltage (V th) of −19.6 V. The maximum current drain density (I D, max) of 249.3 mA/mm was observed with ON-resistance (R ON) of 44.2 V-mm. The electrical results obtained in the vertical mode were also compared with the laterally oriented devices. The comparison of the electrical results indicates a relatively higher ON-resistance of the device in the vertical configuration, due to the contribution of the series resistance of the buffer layers in the epi-structure.

Al x In y Ga ( 1 − x − y ) N / GaN heterostructures were grown on 4-in. p-type Si wafers to investigate the effect of In composition in the quaternary nitride layer on the electrical performance of Al2O3/AlInGaN/GaN-based normally-ON metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs). From the comparative study of the electrical measurements, it was observed that the transport properties of the devices were relatively poor in the presence of higher In composition in the quaternary-N layer. The deterioration of the electrical characteristics of MIS-HEMTs originated from the formation of deep pits on the AlInGaN epilayer surface caused by the segregation of In atoms during epitaxial growth. However, the formation of such pits was reduced for the quaternary epilayer with lower In content and exhibited better transport performance. A maximum current density (Id,max) of 780 mA/mm with a specific ON-resistance of 0.71mΩcm2 was observed for the device fabricated on the wafer with an In composition of 9% in the AlInGaN epilayer. We have achieved a high breakdown voltage of 793 V with a device with the gate-to-drain distance (Lgd) of 20μm under the off-state condition.

We report the fabrication of fully-vertical GaN-based metal-oxide-semiconductor field-effect transistors (V-MOSFETs) on Si. A p-GaN current aperture was introduced in the vertical device epi-structure using plasma-based dry etching and epitaxial regrowth technique to control the vertical current conduction. The fabricated V-MOSFET exhibited drain current density of 2.5 kA cm −2 with ON-resistance (R ON ) of 4.3 mΩ-cm 2 . The transfer characteristics of the device showed a peak trans-conductance (G m,max ) of 248 S cm −2 with a threshold voltage (V th ) of −18.7 V during OFF-to-ON-state sweeping. However, a blocking voltage of 36.5 V (drain current density 0.3 kA cm −2 ) was observed under an OFF-state condition of the device which needs further improvement for the high-power device applications.

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