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Atomic Layer Deposited (ALD) Dielectrics on III-Nitride Devices

III-Nitride metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) and field effect transistors (MISFETs) have gained much attention due to their potential for energy-efficient power switching and high frequency devices.

The interface properties of Al2O3 and GaN (AlGaN) were investigated. The energy band line-up of ALD Al2O3 and GaN (ΔEC=2.1 eV) and substantial amount of positive interface fixed charges (1.83x1013 cm-2) were found experimentally. In MISHEMT structure, the high density of interface fixed charges can act as remote scattering centers, and thus decrease electron mobility especially when the channel is close (several nm) from the fixed charges. Furthermore, the interface fixed charges can shift the threshold voltage to prevent normally-off operation.

An efficient approach to engineer the dielectric/AlGaN (AlN or GaN) positive interface fixed charges by oxygen plasma and post metallization anneal (PMA). Significant suppression of interface fixed charges was observed. The reduction in oxide/semiconductor interface charge density leads to an increase of electron mobility, and enables a positive threshold voltage.

PUBLICATIONS

1) Michele Esposto, Sriram Krishnamoorthy, Digbijoy N. Nath, Sanyam Bajaj, Ting-Hsiang Hung, Siddharth Rajan, "Electrical properties of atomic layer deposited aluminum oxide on gallium nitride", Applied Physics Letters, Vol. 99, 133503 (2011).

2) Ting-Hsiang Hung, Michele Esposto, Siddharth Rajan, “Interfacial charge effects on electron transpore in III-Nitride metal insulator semiconductor transistors”, Applied Physics Letters, Vol. 99, 102104 (2011).

3) Ting-Hsiang Hung, Sriram Krishnamoorthy, Michele Esposto, Digbijoy N. Nath, Pil Sung Park, Siddharth Rajan, "Interface charge engineering at atomic layer deposited dielectric/III-nitride interfaces", Applied Physics Letters, Vol. 102, 072105 (2013).

4) Ting-Hsiang Hung, Pil-Sung Park, Sriram Krishnamoorthy, Digbijoy Nath, Siddharth Rajan, “Interface Charge Engineering for Enhancement-Mode GaN MISHEMTs”, IEEE Electron Device Letters, Vol. 35, No. 3, 99. 312-314, March 2014.