Normally-off p-GaN gate double channel HEMT and the manufacturing method thereof

A method for fabricating high electron mobility transistor (HEMT) device capable of suppressing hot electron induced dynamic on-resistance (RON) degradation, the method comprising:

• preparing a substrate;
• and
• forming a semiconductor stack on the substrate, wherein forming the semiconductor stack comprises:
• forming a lower channel layer;
• forming an insertion layer (ISL) above the lower channel layer for confining electrons in the lower channel layer, thereby to create a first wide bandgap heterojunction between the lower channel layer and the ISL;
• forming an upper channel layer on the ISL, wherein the upper channel layer contacts the ISL;
• forming an interface enhancement layer (IEL) above the upper channel layer for confining the electrons in the upper channel layer, thereby to create a second wide bandgap heterojunction between the upper channel layer and the IEL;
• and
• forming a barrier layer above the IEL,
• wherein:
• the ISL and the IEL each provides a higher energy band with a potential barrier with respect to the electrons generated between the ISL and the lower channel layer, and between the IEL and the upper channel layer;
• and
• the potential barrier prevents or reduces a flow of hot electrons moving from the lower channel layer to the barrier layer:
• wherein the method further comprises forming a gate electrode,
• wherein forming the semiconductor stack further comprises:
• forming a p-type cap such that the p-type cap is sandwiched between the barrier layer and the gate electrode for realizing a normally-off operation,
• wherein the p-type cap is provided without a recess-etching into the barrier layer such that the HEMT device has a planar top p-GaN gate and the upper channel layer is a pristine upper channel layer;
• wherein a thickness of the ISL layer and the IEL layer ranges between 0.5 nm to 2 nm.