Depletion- and Enhancement-Mode p-Channel MISHFET Based on GaN/AlGaN Single Heterostructures on Sapphire Substrates

We report on p-channel metal-insulator-semiconductor heterostructure field-effect transistors (MISHFET) based on p-GaN/uid-GaN/Al0.29Ga0.71N single heterostructures on sapphire substrates, grown by metalorganic vapor phase epitaxy similar to MOVPE). The impact of p-GaN layer removal and channel layer thickness adjustment by dry-etching on the characteristics of the MISHFET are investigated. Depending on the remaining GaN thickness (t(GaN)), the fabricated MISHFET show either depletion-mode (d-mode) operation with a threshold voltage V-th of 3.8 V and an on-current |I-D,I-on| of 9.5 mA/mm (t(GaN) = 21 nm) or enhancement-mode (e-mode) operation with V-th of -2.3 V and |I-D,I-on| of 1.5 mA/mm (t(GaN) = 12 nm). Independent of the etching depth, all devices exhibit a very low off-state drain current |I-D,I-off|similar to 10(-8) mA/mm and a steep subthreshold swing (SS) between 80 and 89 mV/dec. Similar to n-channel devices, a V-th instability caused by charge trapping at the dielectric/semiconductor interface is found, emphasizing that careful interface engineering is required for good device performance.

Automated summary

This paper reports on the study of p-channel metal-insulator-semiconductor heterostructure field-effect transistors (MISHFET) based on p-GaN/uid-GaN/Al0.29Ga0.71N single heterostructures. The impact of p-GaN layer removal and channel layer thickness adjustment on the characteristics of the MISHFET is investigated. The results show that the fabricated devices exhibit either depletion-mode or enhancement-mode operation, depending on the remaining GaN thickness.