Identification of Trap States in p-GaN Layer of a p-GaN/AlGaN/GaN Power HEMT Structure by Deep-Level Transient Spectroscopy

• Published in: IEEE electron device letters Vol. 41; no. 5; pp. 685 - 688
• Main Authors: Yang, Song, Huang, Sen, Wei, Jin, Zheng, Zheyang, Wang, Yuru, He, Jiabei, Chen, Kevin J.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.05.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: <italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">p -GaN/AlGaN/GaN heterojunction; Activation energy; Aluminum gallium nitrides; Capacitance; Capacitance deep-level transient spectroscopy (C-DLTS); Capacitors; Deep level transient spectroscopy; Electron traps; Energy levels; Gallium nitrides; HEMTs; Heterojunctions; High electron mobility transistors; hole insufficiency; Hole traps; Junctions; Logic gates; Semiconductor devices; Spectrum analysis; Threshold voltage; Transient analysis; trap states
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2020.2980150

In this work, the deep-level transient spectroscopy (DLTS) is conducted to investigate the gate stack of the <inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN gate HEMT with Schottky gate contact. A metal/<inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN/AlGaN/GaN heterojunction capacitor is prepared for the study. The DLTS characterization captures the transient capacitance change in the stack, from which the capacitance of the metal/<inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN Schottky junction can be extracted. By proper selection of the rate window, the impacts of the hole insufficiency effect are avoided during trap states evaluation. Thus, the information of deep energy levels in the <inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN layer is revealed, which consists of an electron trap state with activation energy of 0.85 eV and a hole trap state with activation energy of 0.49 eV. The identification of these trap states in the <inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN layer provides a physical foundation for understanding the threshold voltage instability in Schottky-type <inline-formula> <tex-math notation="LaTeX">{p} </tex-math></inline-formula>-GaN gate power HEMTs.