Enhancement-mode switching device and preparation method therefor
Disclosed are an enhancement-mode switching device and a preparation method therefor. The enhancement-mode switching device includes: a substrate; a channel structure; an n-type semiconductor layer covering a bottom wall of the trench; a p-type semiconductor layer arranged in a gate region; a gate electrode arranged on a side, away from the substrate, of the p-type semiconductor layer; a source electrode arranged in a source region; a drain electrode arranged in a drain region. In the gate region, the p-type semiconductor layer and n-type semiconductor layer are in contact with each other to form a space depletion region in the gate region, and the electronic channel between the source electrode and the drain electrode of the switching device is interrupted, so that the switching device may be effectively turned off under a gate bias voltage of zero, improving control capability of the gate electrode and reliability of the device.
1 . An enhancement-mode switching device, comprising:
a substrate;
a channel structure comprising a channel layer and a barrier layer, wherein the channel layer is arranged on the substrate, and the barrier layer is arranged on a side, away from the substrate, of the channel layer; a trench is provided on a side, away from the substrate, of the channel structure, and the trench penetrates through the channel structure along a thickness direction of the channel structure and reaches a bottom of the channel layer; the channel structure comprises a source region, a drain region, and a gate region located between the source region and the drain region; and the trench is arranged in the gate region;
an n-type semiconductor layer covering a bottom wall of the trench;
a p-type semiconductor layer, wherein the p-type semiconductor layer is arranged, in the gate region, on the n-type semiconductor layer, and at least a partial area of the p-type semiconductor layer is arranged in the trench; the p-type semiconductor layer comprises at least one composition changing element, a content of the composition changing element changes in an epitaxial direction, and a changing curve of the content of the composition changing element in the epitaxial direction comprises one or more changing stages and the changing stages comprise: periodic changing, progressive increasing and progressive decreasing;
wherein the p-type semiconductor layer is a periodic structure, and the periodic structure comprises at least one period stacked sequentially in the epitaxial direction, each period comprises a first periodic layer and a second periodic layer stacked sequentially in the epitaxial direction;
in the epitaxial direction, a content, in the first periodic layer, of the composition changing element increases at an uniform speed and a content, in the second periodic layer, of a composition changing element decreases at an uniform speed in the epitaxial direction; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed and the content, in the second periodic layer, of the composition changing element increases at an uniform speed; or
in the epitaxial direction, a first content, in the first periodic layer, of the composition change element is constant, and a second content, in the second periodic layer, of the composition change element is constant, the first content is higher than the second content, or the first content is lower than the second content; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element increases at an uniform speed, and the content, in the second periodic, of the composition changing element is constant; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed, and the content, in the second periodic layer, of the composition changing element is constant;
a gate electrode arranged on a side, away from the substrate, of the p-type semiconductor layer;
a source electrode arranged in the source region; and
a drain electrode arranged in the drain region.
2 . The enhancement-mode switching device according to claim 1 , wherein the n-type semiconductor layer covers the bottom wall and sidewalls of the trench, and the p-type semiconductor layer is arranged on the n-type semiconductor layer.
3 . The enhancement-mode switching device according to claim 2 , wherein the channel structure is a multi-channel structure comprising k layers of the channel layers and k layers of the barrier layers alternately arranged, wherein k≥2.
4 . The enhancement-mode switching device according to claim 1 , wherein a material of the n-type semiconductor layer comprises one or more of n-type GaN, n-type AlGaN and n-type InGaN.
5 . The enhancement-mode switching device according to claim 1 , wherein a doping concentration of p-type impurity ions in the p-type semiconductor layer changes, from bottom to top, in one or more modes and the modes comprise:
gradually increasing, gradually decreasing, step-type increasing, step-type decreasing and periodic changing.
6 . The enhancement-mode switching device according to claim 1 , wherein a material of the p-type semiconductor layer comprises one or more of p-type GaN, p-type AlGaN and p-type InGaN.
7 . The enhancement-mode switching device according to claim 1 , wherein the trench comprises a plurality of discrete trenches.
8 . The enhancement-mode switching device according to claim 1 , further comprising:
a back barrier layer, arranged on a side, facing toward the substrate, of the channel layer.
9 . The enhancement-mode switching device according to claim 8 , wherein the back barrier layer is an n-type semiconductor layer.
10 . The enhancement-mode switching device according to claim 1 , further comprising a cap layer arranged on a side, away from the substrate, of the barrier layer, and the cap layer being provided with an opening communicating with the trench.
11 . The enhancement-mode switching device according to claim 1 , further comprising an N-type heavily doped nitride semiconductor arranged in the source region and the drain region.
12 . An enhancement-mode switching device, comprising:
a substrate;
a channel structure comprising a channel layer and a barrier layer, wherein the channel layer is arranged on the substrate, and the barrier layer is arranged on a side, away from the substrate, of the channel layer; a trench is provided on a side, away from the substrate, of the channel structure, and the trench penetrates through the channel structure along a thickness direction of the channel structure and reaches a bottom of the channel layer; the channel structure comprises a source region, a drain region, and a gate region located between the source region and the drain region; and the trench is arranged in the gate region;
an n-type semiconductor layer arranged on a surface, facing toward the substrate, of the channel layer, wherein a p-type semiconductor layer is formed on the n-type semiconductor layer exposed by the trench; the p-type semiconductor layer comprises at least one composition changing element, a content of the composition changing element changes in an epitaxial direction, and a changing curve of the content of the composition changing element in the epitaxial direction comprises one or more changing stages and the changing stages comprise: periodic changing, progressive increasing and progressive decreasing;
wherein the p-type semiconductor layer is a periodic structure, and the periodic structure comprises at least one period stacked sequentially in the epitaxial direction, each period comprises a first periodic layer and a second periodic layer stacked sequentially in the epitaxial direction;
in the epitaxial direction, a content, in the first periodic layer, of the composition changing element increases at an uniform speed and a content, in the second periodic layer, of a composition changing element decreases at an uniform speed in the epitaxial direction; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed and the content, in the second periodic layer, of the composition changing element increases at an uniform speed; or
in the epitaxial direction, a first content, in the first periodic layer, of the composition change element is constant, and a second content, in the second periodic layer, of the composition change element is constant, the first content is higher than the second content, or the first content is lower than the second content; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element increases at an uniform speed, and the content, in the second periodic, of the composition changing element is constant; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed, and the content, in the second periodic layer, of the composition changing element is constant;
a gate electrode, arranged on a side, away from the substrate, of the p-type semiconductor layer;
a source electrode, arranged in the source region; and
a drain electrode, arranged in the drain region.
13 . A preparation method for an enhancement-mode switching device, comprising:
providing a substrate;
forming a channel structure, wherein the channel structure comprises a channel layer and a barrier layer, the channel layer is arranged on the substrate, and the barrier layer is arranged on a side, away from the substrate, of the channel layer; the channel structure comprises a source region, a drain region, and a gate region located between the source region and the drain region; and the trench is arranged in the gate region;
arranging a trench on a side, away from the substrate, of the channel structure, wherein the trench penetrates through the channel structure along a thickness direction of the channel structure and reaches a bottom of the channel layer, and the trench is arranged in the gate region;
forming an n-type semiconductor layer covering a bottom wall of the trench;
forming a p-type semiconductor layer on the n-type semiconductor layer, wherein at least a partial area of the p-type semiconductor layer is arranged in the trench; the p-type semiconductor layer comprises at least one composition changing element, a content of the composition changing element changes in an epitaxial direction, and a changing curve of the content of the composition changing element in the epitaxial direction comprises one or more changing stages and the changing stages comprise: periodic changing, progressive increasing and progressive decreasing;
wherein the p-type semiconductor layer is a periodic structure, and the periodic structure comprises at least one period stacked sequentially in the epitaxial direction, each period comprises a first periodic layer and a second periodic layer stacked sequentially in the epitaxial direction;
in the epitaxial direction, a content, in the first periodic layer, of the composition changing element increases at an uniform speed and a content, in the second periodic layer, of a composition changing element decreases at an uniform speed in the epitaxial direction; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed and the content, in the second periodic layer, of the composition changing element increases at an uniform speed; or
in the epitaxial direction, a first content, in the first periodic layer, of the composition change element is constant, and a second content, in the second periodic layer, of the composition change element is constant, the first content is higher than the second content, or the first content is lower than the second content; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element increases at an uniform speed, and the content, in the second periodic, of the composition changing element is constant; or
in the epitaxial direction, the content, in the first periodic layer, of the composition changing element decreases at an uniform speed, and the content, in the second periodic layer, of the composition changing element is constant;
forming a gate electrode on a side, away from the substrate, of the p-type semiconductor layer;
forming a source electrode in the source region; and
forming a drain electrode in the drain region.
14 . The preparation method for the enhancement-mode switching device according to claim 13 , wherein the forming an n-type semiconductor layer covering a bottom wall of the trench comprises:
forming the n-type semiconductor layer covering the bottom wall and sidewalls of the trench.
15 . The preparation method for the enhancement-mode switching device according to claim 14 , wherein the forming a channel structure comprises:
forming a multi-channel structure comprising k layers of channel layers and k layers of barrier layers alternately arranged, wherein k≥2.
16 . The preparation method for the enhancement-mode switching device according to claim 13 , further comprising:
forming a back barrier layer on a side, facing toward the substrate, of the channel layer.