BACKGROUND

Technical Field

The present disclosure relates to an HEMT device and to a method for manufacturing the same.

Description of the Related Art

Known to the art are high-electron-mobility transistors (HEMTs) with heterostructure made, in particular, of gallium nitride (GaN) and aluminum gallium nitride (AlGaN). For example, HEMT devices are appreciated for use as power switches thanks to their high breakdown threshold. In addition, the high current density in the conductive channel of the HEMT enables a low ON-state resistance (RON) of the conductive channel.

In order to favor use of HEMTs in high-power applications, recessed-gate HEMTs have been introduced.

A problem with devices of this type regards the drastic reduction of current, due to an increase of the ON-state resistance (RON), during switching operations. The temporary increase in the RONvalue after high-voltage biasing (400-600 V) in the OFF state is deemed to be caused by an excessive trapping of the charge carriers in the channel, in the buffer layer, or at the surface.

In order to reduce this problem, various solutions have been adopted.

The document by D. Jin et al., “Total current collapse in High-Voltage GaN MIS-HEMTs induced by Zener trapping”, Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Mass., U.S.A., represents a method of control of defects during the stage of epitaxial growth of the channel and an appropriate design of the “field plate” structures. This method, however, does not solve the problem and requires a control of the growth stage, which has an impact on the costs of industrial production of HEMTs.

The document by P. Moens et al., “On the Impact of Carbon-Doping on the Dynamic Ron and Off-state Leakage Current of 650V GaN Power Devices”, ON Semiconductor, suggests that the optimization of the doping profile with carbon atoms of the semiconductor body of the HEMT at the level of the buffer layer may provide a solution to the aforementioned problem. However, the presence itself of impurities such as carbon atoms may itself be the cause of further trapping of carriers and RONdegradation.

The document by J. Würfl et al., “Techniques towards GaN power transistors with improved high voltage dynamic switching properties”, 2013, discusses the limitation of dynamic switching in a GaN power device and proposes techniques for improving fast switching at high voltage by modifying the structure of the buffer layer of an HEMT. The aforementioned problems, however, are not solved.

BRIEF SUMMARY

At least some embodiments of the present disclosure provide an HEMT device and a manufacturing method thereof that are alternative to the ones proposed according to the prior art, and that overcome the drawbacks set forth above.

According to at least one embodiment of the present disclosure, an HEMT device includes:

a semiconductor body including a heterojunction structure that forms a main conductive channel of the HEMT device;

a dielectric layer on the semiconductor body;

a gate electrode, a drain electrode, and a source electrode aligned with one another in a direction, wherein the drain electrode extends facing a first side of the gate electrode, and the source electrode extends facing a second side, opposite to the first side in said direction, of the gate electrode; and

an auxiliary channel layer, which extends over the heterojunction structure between the gate electrode and the drain electrode, is in electrical contact with the drain electrode, is spaced apart from the gate electrode, and forms a conductive path additional to the main conductive channel for charge carriers that flow between the source electrode and the drain electrode.

