Date of Graduation

8-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Mantooth, H. Alan

Committee Member

Salamo, Gregory J.

Second Committee Member

Francis, A. Matthew

Third Committee Member

Ware, Morgan E.

Keywords

Compact Modeling; Gallium Nitride; Power Electronics; Power Semiconductor Devices; Semi-conductor Device Modeling; Wide Band Gap Devices

Abstract

Gallium Nitride is a relatively new material compound compared to Silicon that has demonstrated immense promise as a material for power semiconductor devices. Silicon based power semiconductor devices have already reached very close their theoretical limits and it may not be possible to extract any further efficiency improvements out of these devices. Lateral GaN devices have already penetrated the power electronics market with breakdown voltages up to 650 V. Theoretically, gallium nitride has already demonstrated excellent figure of merit compared to silicon and silicon carbide. Currently, compact models that can predict the performance characteristics of a wide range of lateral GaN devices are not readily available. The models currently available are semi-empirical/empirical SPICE models or physical models for RF GaN devices.

This work presents a compact GaN device model that can predict the performance characteristics of a wide range of commercial GaN devices. The model has been validated against the characteristics of medium voltage-range EPC devices and high-voltage range Panasonic GaN devices. The medium-voltage range devices do not have any significant drift resistance in their on-state behavior while the high-voltage range devices exhibit significant non-linear drift resistance which is evident from their on-state behavior. The medium-voltage range devices have non-linear reverse capacitance due to the depletion region. The high-voltage GaN device have significant non-linear capacitance behavior due to the existence of field-plates connected to the source and drain. The field-plates are fabricated to augment the electric-field distribution in the channel. However, field plates result in significant non-linearity in the channel which can be seen as successive depletion in the device capacitances. These effects are accurately characterized by the proposed model in this work. The model also captures the third-quadrant behavior of all GaN devices with the model parameters that are de-coupled from the first quadrant while maintaining continuity between the first and third quadrant. The model also captures the temperature dependent device characteristics. The convergence capability of the model is also verified using various power electronics topologies.

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