Abstract
In this paper, the analytical models of breakdown voltage design parameters and minimum specific on-resistance in vertical gallium nitride unipolar devices are proposed. Considering the discrepancy of the impact ionization coefficients (IIC) reported in previous literatures from the Monte Carlo simulations and experiments, the analytical models of avalanche breakdown of gallium nitride devices both in punch-through and non-punch-through conditions are presented, i.e., the relationship between the breakdown voltage, drift doping concentration, drift thickness and critical electric field, which shows high accuracy with the results from numerical simulations. The comparison with the reported experimental results demonstrates the comparatively higher accuracy of the IIC data from Baliga. Taking into account the incomplete ionization in dopant impurities in GaN, the tradeoff between specific on-resistance and breakdown voltage is also given, demonstrating the optimized punch-through design has minimum specific on-resistance, which can be reduced by up to 12% for breakdown voltage from 1 kV to 15 kV. Meanwhile, the corresponding drift thickness can be reduced by from 18% to 20%, which can largely reduce the fabrication cost of epitaxial growth. The proposed optimized relationship is in good accordance with the results from MEDICI simulations.
Highlights
Gallium nitride (GaN) power switching devices are promising as ideal candidates in the high power and high frequency applications, leveraging the well-recognized advantageous wide-band-gap material properties such as high breakdown field strength, high electron mobility, high electron saturation velocity and high working temperature [1], [2]
In the GaN unipolar devices such as MOSFETs and SBDs, a high breakdown voltage coupled with a low specific onresistance is highly desired from the viewpoint of power loss
The modeling and design of breakdown voltage (BV) are based on the impact ionization coefficient (IIC), whose accuracy can be verified by comparing BVs both from theoretically calculation and from their experiment measurements
Summary
Gallium nitride (GaN) power switching devices are promising as ideal candidates in the high power and high frequency applications, leveraging the well-recognized advantageous wide-band-gap material properties such as high breakdown field strength, high electron mobility, high electron saturation velocity and high working temperature [1], [2]. The modeling and design of breakdown voltage (BV) are based on the impact ionization coefficient (IIC), whose accuracy can be verified by comparing BVs both from theoretically calculation and from their experiment measurements. Comparisons are made with the reported experimental results to evaluate different IICs. In Sec. III, the design parameters for PT and NPT conditions are discussed, and minimum specific on-resistance including the incomplete ionization effect for the optimized PT condition are determined. As is evident from the preceding discussion, the approach proposed here is very efficient to verify the accuracy by comparing the experimental and the calculated BVs. In section, based on Baliga’s experimental IIC, the design parameters with analytical expressions targeting a minimum specific on-resistance will be presented
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