Open AccessImprovement in breakdown characteristics of 4H-SiC MESFET with a gate-drain surface epi-layer and optimization of the structure
Author(s) -
Kun Song,
Changchun Chai,
Yong Yang,
Xianjun Zhang,
Chen Bin
Publication year - 2012
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.61.027202
Subject(s) - mesfet , electric field , materials science , breakdown voltage , doping , optoelectronics , voltage , surface layer , saturation (graph theory) , layer (electronics) , condensed matter physics , field effect transistor , transistor , composite material , electrical engineering , physics , mathematics , engineering , quantum mechanics , combinatorics
A novel SiC MESFET structure with a p-type surface epi-layer is proposed and 4H-SiC MESFET models are presented which precisely describe the working mechanism of the device. Considering carrier velocity saturation, impact ionization and electric field modulation, the effect on distribution of electric field is analyzed. Also, the output current (Ids) and breakdown voltage (VB) dependences on the dimensions of the p-type epi-layer are studied based on abrupt junction approximation. The high electric field peak at the gate edge is suppressed by introducing a new electric field peak at the drain side, and the built-in field of p-n junction formed along channel surface further weakens the electric field peaks, leading to smoother distribution of electric field. By comparison with the conventional and the fieldplated MESFETs, it is shown that the proposed structure greatly improves the characteristic of SiC MESFET. In addition, the optimized dimensions are obtained and the results show that VB is greatly increased by 33% with Ids unchanged (less than 3%) when the thickness and the doping concentration of the surface epi-layer are chosen as 0.12 upm and 5 1015 cm-3, respectively.