Vertical GaN-based Heterojunction Field-Effect Transistor with Charge Compensation and Withstand Voltage Structure

Abstract

The invention discloses a vertical gallium nitride-based heterojunction field effect transistor with a charge compensation withstand voltage structure. The special feature of the device is that it also includes charges located outside the barrier layer, channel layer, current blocking layer and n-GaN buffer layer. Compensation insulating layer, and high-density fixed charges exist at the interface between the charge compensation insulating layer and the barrier layer, channel layer, current blocking layer and n-GaN buffer layer; the charge compensation insulating layer is made of insulating dielectric. Due to the high density of fixed charges at the interface between the charge compensation insulating layer and the n-GaN buffer layer, the negative charge on the interface can make the adjacent n-GaN buffer layer invert when the voltage is withstand, and the formed p+ column will consume the n-GaN buffer layer The electrons in the buffer layer form a p+n superjunction structure and are completely depleted. After fully optimizing, the electric field in the buffer layer can maintain 3MV / cm in the vertical direction and basically remain unchanged, and the breakdown voltage of the device reaches the withstand voltage limit of GaN materials. .

Description

technical field [0001] The invention relates to the field of semiconductor high withstand voltage devices, in particular to a vertical GaN-based heterojunction field effect transistor with a charge compensation withstand voltage structure. Background technique [0002] GaN Heterojunction Field-Effect Transistor (GaN HFET) not only has a large band gap, a high critical breakdown electric field, a high electron saturation velocity, good thermal conductivity, radiation resistance and good chemical stability At the same time, gallium nitride (GaN) materials can form a two-dimensional electron gas heterojunction channel with high concentration and high mobility with materials such as aluminum gallium nitride (AlGaN), so it is especially suitable for high voltage, high power and It is one of the most potential transistors for power electronics applications for high temperature applications. [0003] The existing high withstand voltage GaN HFET structure is mainly a lateral device...

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Problems solved by technology

[0005] For the conventional GaN VHFET structure, the device mainly relies on the p-n junction formed between the p-GaN current blocking layer and the n-GaN buffer layer to withstand the withstand voltage. When the peak electric field in the device reaches the critical electric field or the leakage current reaches the threshold, the n- The width of the depletion region in the GaN buffer layer determines the breakdown voltage of the device. As the thickness of the n-GaN buffer layer increases, the width of the depletion region in the n-GaN also increases during breakdown. However, when When the thickness of the n-GaN buffer layer exceeds a certain value, the width of the depletion region in the n-GaN reaches saturation during breakdown, and the breakdown voltage of the device also reaches saturation, and no longer increases with the thickness of the n-GaN buffer layer. large, which limits the high withstand voltage applications of GaN VHFETs

At the same time, the vertical electric field intensity in the n-GaN buffer layer will gradually decrease as it moves away from the p-n junction interface between the p-GaN current blocking layer and the n-GaN buffer layer. The integral of the vertical electric field strength along the vertical direction, the decreasing vertical electric field strength makes the breakdown voltage of the device unable to reach the GaN material limit, and cannot fully utilize the high withstand voltage advantages of GaN-based devices

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