{"id":122,"date":"2016-02-16T17:17:19","date_gmt":"2016-02-17T01:17:19","guid":{"rendered":"http:\/\/www.ece.ucdavis.edu\/mdasl\/?page_id=122"},"modified":"2016-02-16T17:17:19","modified_gmt":"2016-02-17T01:17:19","slug":"bandgap_modeling","status":"publish","type":"page","link":"https:\/\/www.ece.ucdavis.edu\/mdasl\/research\/bandgap_modeling\/","title":{"rendered":"Empirical Modeling of High Power Wide Bandgap Microwave Semiconductor Devices"},"content":{"rendered":"

Wide bandgap semiconductor devices such as GaN HEMTs and SiC MESFETs have a growing presence in high power microwave electronics applications. Computer aided design of high power microwave circuits gives rise to the need for accurate large-signal models. However, nonidealities such as charge-trapping and thermal self-heating make understanding and modeling these devices a challenge. A methodology to characterize and model the dispersive effects that plague such devices is investigated.\u00a0 Development of a large-signal drain current model predicting the effects of trapping and thermal self-heating is explored for these devices. Complete nonlinear models for GaN HEMTs and SiC MESFETs accurately predicting IV, small-signal and large-signal RF behavior under various quiescent bias and frequency conditions are investigated.<\/span><\/p>\n

Model Topology and Challenges<\/span><\/b><\/p>\n

The objective is to develop a general-purpose model which accurately predicts dynamic IV characteristics, large-signal RF power and S-parameters under varying thermal and bias conditions.<\/span><\/p>\n

The most important aspects of these high-power devices is the characterization of self-heating and charge-trapping effects on the device and their effect on drain current performance.<\/span><\/p>\n

The generalized large-signal model topology shown here and the numerous aspects of which constitute the model are shown.<\/span><\/p>\n

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Dynamic IV Techniques<\/span><\/b><\/p>\n

SiC MESFET Nonlinear Drain Current Model<\/span><\/i><\/p>\n

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GaN HEMT Nonlinear Drain Current Model<\/span><\/i><\/p>\n

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Implementation of Self-Heating and Charge-Trapping into Ids<\/span><\/b><\/p>\n

The two main types of charge-trapping: surface trapping and substrate trapping; are exploited using PIV characteristics at various biases. The charge trapping effects can be addressed and adjusted for using an effected gate-source voltage modifier.<\/span><\/p>\n

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SiC MESFET Pulsed-IV<\/span><\/i><\/p>\n

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GaN HEMT Pulsed-IV<\/span><\/i><\/p>\n

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Verification of RF performance of model<\/span><\/b><\/p>\n

The accuracy of the complete large-signal models have been verified under small- and large-signal RF drive for several representative biases and over varying power levels and bandwidths. The performance of the model operating under small-signal conditions is shown first. The model is then compared with large-signal multiharmonic output and input reflected power. Finally, the third order intermodulation distortion predictions of the models is presented.<\/span><\/p>\n

Small-Signal S-parameters<\/span><\/b><\/p>\n

Accurate predictions of broadband small-signal behavior over various biases can be seen for both device models. This infers that the gm and gds computed from the pulsed-IV-based, Ids formulations are accurate under small-signal drive. Additionally, the parasitic elements have been correctly extracted from multi-bias S-parameter measurements and that the nonlinear Cgs, Cgd and Cds have been properly treated.<\/span><\/p>\n

SiC MESFET<\/span><\/i><\/p>\n

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GaN HEMT<\/span><\/i><\/p>\n

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Large-Signal RF Measurement<\/span><\/b><\/p>\n

The large-signal multi-harmonic, broadband single-tone and two-tone measurements comparisons are shown below. These include output power (Pout) and input reflected power (Prefl) for three harmonics. The modeled computations show good agreement with measured data.<\/span><\/p>\n

SiC MESFET<\/span><\/i><\/p>\n

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GaN HEMT<\/span><\/i><\/p>\n

\"\"<\/p>\n","protected":false},"excerpt":{"rendered":"

Wide bandgap semiconductor devices such as GaN HEMTs and SiC MESFETs have a growing presence in high power microwave electronics applications. Computer aided design of high power microwave circuits gives rise to the need for accurate large-signal models. However, nonidealities such as charge-trapping and thermal self-heating make understanding and \u2026 Continue reading → <\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":56,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-122","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/pages\/122","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/comments?post=122"}],"version-history":[{"count":0,"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/pages\/122\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/pages\/56"}],"wp:attachment":[{"href":"https:\/\/www.ece.ucdavis.edu\/mdasl\/wp-json\/wp\/v2\/media?parent=122"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}