Design of kV-Class and Low R<sub>ON</sub> E-Mode β-Ga<sub>2</sub>O<sub>3</sub> Current Aperture Vertical Transistors With Delta-Doped β-(AlxGa<sub>1−x</sub>)<sub>2</sub>O<sub>3</sub>/Ga<sub>2</sub>O<sub>3</sub> Heterostructure
Dawei Wang, Dinusha Herath Mudiyanselage, Houqiang Fu
Abstract
This work demonstrated a comprehensive design and modeling of enhancement-mode (E-mode) beta-phase gallium oxide ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3) current-aperture vertical electron transistors (CAVETs) using TCAD simulation. A new <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 CAVET [i.e., high electron mobility transistors (HEMT)-CAVETs] was proposed by introducing delta-doped <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -(AlxGa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{1}-{x}}$ </tex-math></inline-formula> )2O3/Ga2O3 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}= {0.2}$ </tex-math></inline-formula> ) heterostructure into the conventional CAVETs. The HEMT-CAVETs showed significant improvements in electron modulation, ON-state resistance (RON), and leakage due to the confined two-dimensional electron gas (2DEG) channel. The design space of doping, channel length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {ch}}$ </tex-math></inline-formula> ), and aperture length ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {ap}}$ </tex-math></inline-formula> ) on the device threshold voltages ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> ), RON, breakdown voltage (BV), and OFF-state leakage were systematically investigated. With increasing delta-doping concentration, the HEMT-CAVETs showed smaller RON compared with the conventional CAVETs. The OFF-state leakage from the aperture and the current blocking layers (CBLs) in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 CAVETs was studied for the first time. Larger <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {ch}}$ </tex-math></inline-formula> prevented the OFF-state leakage current from the aperture and increased BV, but it also increased RON due to larger channel resistance. Small <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {ap}}$ </tex-math></inline-formula> could dramatically increase device RON due to the encroachment of the aperture by the depletion regions from the CBLs. The CBL breakdown played a key role in the device BV. The BV of the CBL increased with increasing CBL thickness and acceptor doping concentration, where kV-level BV and high peak electric fields of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\sim }8$ </tex-math></inline-formula> MV/cm can be obtained with optimized CBLs. These results can serve as a critical reference for the future development of kV-class low RON <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 CAVETs for high-power, high-voltage, and high-frequency applications.