Browsing by Author "Tseng, Yang-Yan"

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Demonstration of Annealing-free Metal-Insulator-Semiconductor (MIS) Ohmic Contacts on a GaN Substrate using Low Work-function Metal Ytterbium (Yb) and Al2O3 Interfacial Layer
(2019-01-01)
Wu, Tian-Li
;
Tseng, Yang-Yan
;
Huang, Chih-Fang
;
Chen, Zih-Sin
;
Lin, Chih-Chien
In this letter, the Metal-Insulator-Semiconductor (MIS) contacts are fabricated on the GaN substrates and compared to the Metal-Semiconductor (MS) contacts. To alleviate the Fermi level pinning effect at the Metal-Semiconductor interface, an Al2O3 interfacial layer (IL) (1 similar to 3 nm) is used to form the MIS contacts. By comparing the electrical characteristics, the contact with Onm Al2O3 layer, i.e., MS contact, shows a lowest current compared to the contacts with an Al2O3 IL, i.e., MIS contact. Furthermore, the current at 0.5V in the fabricated Transmission Line Measurement (TLM) device with lnm Al2O3 IL is 10(3) times higher the one without an Al2O3 IL. This proves that inserting an Al2O3 IL could mitigate the Fermi level pinning, resulting in a low Schottky barrier height. Finally, based on the TLM analysis, the resistivity of 5.1x10(-4) Omega.cm(2) is demonstrated in the MIS contact with lnm Al2O3 IL.
Investigation of the degradations in power GaN-on-Si MIS-HEMTs subjected to cumulative gamma-ray irradiation
(2019-09-01)
Sharma, Chandan
;
Modolo, Nicola
;
Chen, Hsi-Han
;
Tseng, Yang-Yan
;
Tang, Shun-Wei
In this work, GaN-on-Si power Metal-Insulator-Semiconductor High Electron Mobility Transistors(MIS-HEMTs) are irradiated through different regimes of cumulative gamma-ray irradiation, namely 1, 2, 3, 4, and 5 kGy for the first sample; 1, 3, and 5 kGy for the second sample; 1, 5, and 10 kGy for the third sample; and 1, 10, and 20 kGy for the fourth sample. After each irradiation dose, drain current (ID), threshold voltage (I-g), and gate leakage current (Is) are electrically characterized in all the samples. An improvement in I-D with a shift in V-Th is observed in all the samples, which saturates after a higher irradiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirms creation of nitrogen vacancies that act as donor and improves the I-D. No significant change in I-g is observed except for an increase in noise in gate leakage current. Scanning electron microscopy (SEM) shows the Al-based metallization pad degrades due to formation of small cavities. Finally, energy dispersive X-ray (EDX) analysis confirms the formation of Al native oxides due to gamma-ray irradiation.