Characterization of AlGaN/GaN and AlGaN/AlN/GaN HEMTs in terms of mobility and subthreshold slope

• Published in: Journal of computational electronics 2016-03, Vol.15 (1), p.172-180
• Main Authors: Prasad, Santashraya, Dwivedi, Amit Krishna, Islam, Aminul
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitrides; Aluminum nitride; Current carriers; Efficiency; Electrical Engineering; Electron gas; Electronics; Electrons; Engineering; Gallium nitrides; High electron mobility transistors; Mathematical and Computational Engineering; Mathematical and Computational Physics; Mechanical Engineering; Optical and Electronic Materials; Semiconductor devices; Semiconductors; Simulation; Slopes; Spacers; Theoretical; Transconductance; Transistors
• ISSN: 1569-8025; 1572-8137
• DOI: 10.1007/s10825-015-0751-8

This paper presents two structures of wide band gap high electron mobility transistor (HEMT). One structure is made-up of a stack of AlGaN layer over GaN layer. This structure is characterized by two-dimensional (2-D) electron gas layer formed at the interface of the AlGaN and GaN layers. The 2-D electron gas plays an important role in determining the carrier-mobility ( μ ) and hence drain-to-source current ( I DS ) of HEMT. The other structure introduces an AlN spacer layer between the AlGaN and GaN layers to improve these characteristics. This paper compares the output characteristics curves ( I DS - V DS ) and transconductance characteristics curves ( I DS - V GS ) obtained from simulations performed using Silvaco ATLAS TM . The modified structure with spacer layer shows improvements in carrier-mobility and hence drain-to-source current. This paper estimates and compares the subthreshold slope (SS) of the two devices. AlGaN/AlN/GaN HEMT offers an SS of 80 mV/decade whereas AlGaN/GaN HEMT offers an SS of 95 mV/decade. Thus, an improvement in SS of about 18.75 % is achieved in AlGaN/AlN/GaN HEMT compared to AlGaN/GaN HEMT. HEMT with spacer layer also offers 10 × improvement in I D S as compared to HEMT without spacer layer. The proposed HEMTs achieve ≈ 3.19 × improvement in breakdown voltage, > 1.3 × improvement in SS compared to HEMTs previously proposed in the literature.