High-temperature studies of multiple fluorinated traps within an Al2O3 gate dielectric for E-Mode AlGaN/GaN power MIS-HEMTs. (7th December 2015)

• Record Type: Journal Article
• Authors: Wang, Yun-Hsiang; Liang, Yung C; Samudra, Ganesh S; Chu, Po-Ju; Liao, Ya-Chu; Huang, Chih-Fang; Kuo, Wei-Hung; Lo, Guo-Qiang
• Is Part Of: Semiconductor science and technology. Volume 31:Number 2(2016:Feb.)
• Publication Date: 2015-12-07
• Subjects: fluorine plasma treatment -- normally-off -- Al2O3/AlGaN/GaN -- power HEMT -- threshold swing -- high-temperature threshold stability; Semiconductors -- Periodicals; 621.38152
• DOI: 10.1088/0268-1242/31/2/025004
• Languages: English
• ISSNs: 0268-1242

Abstract

Abstract: Normally-off AlGaN/GaN MIS-HEMT devices with multiple fluorinated ALD-Al2 O3 layers as the gate dielectric have been reported to achieve a high threshold voltage for normally-off operations with satisfactory performance for both on and off states at room temperature. However, a large swing in gate threshold voltage is found when devices operate at elevated temperatures. Hence, further study of the gate dielectric on the distribution of fluorinated trap states in the energy band are required to assess the gate function at higher temperatures. Through the use of the charge analytical model and Poole–Frenkel trap emission theory, the gate voltage stressing measurement was carried out to accurately find the effective trap state distribution within the Al2 O3 energy bandgap created by fluorinated treatments. For the samples fabricated and used in the investigation, we found that a higher population of fluorinated trap states located deeper than 1.1 eV corresponding to emission levels above 200 °C would allow more trapped charges to remain in the dielectric at high temperature for better threshold voltage retention. We also discovered that a higher fluorine treatment power on the gate dielectric could yield a higher trap state density at deeper levels, resulting in better temperature stability.