Electric field management for a group III-nitride semiconductor device
A semiconductor device includes a substrate, a first active layer, a second active layer, at least first and second electrodes, an E-field management layer, and at least one injection electrode. The first active layer is disposed over the substrate. The second active layer is disposed on the first active layer such that a laterally extending conductive channel arises which extends in a lateral direction. The laterally extending conductive channel is located between the first active layer and the second active layer. The first and second electrodes are electrically connected to the first active layer. The E-field management layer, which reduces the electric-field gradients arising in the first and second active layers, is disposed over the second active layer. The injection electrode is electrically connected to the E-field management layer.
1. A semiconductor device, comprising:
a substrate;
a first active layer disposed over the substrate;
a second active layer disposed on the first active layer such that a laterally extending conductive channel arises which extends in a lateral direction, the laterally extending conductive channel being located between the first active layer and the second active layer;
first and second electrodes electrically connected to the first active layer;
an E-field management layer for reducing electric-field gradients arising in the first and second active layers, the E-field management layer being disposed over the second active layer, the E-field management layer having a resistivity greater than 1 kΩ×cm;
an injection electrode electrically connected to the E-field management layer;
wherein the first and second electrodes are source and drain electrodes, respectively, and further comprising a gate electrode disposed completely in a recess extending into the E-field management layer above an upper surface of the second active layer between the source electrode and the drain electrode,
wherein the injection electrode is disposed between the gate electrode and the drain electrode extending laterally towards the drain electrode without any electrical connection with either the source electrode, the drain electrode or the gate electrode.
2. The semiconductor device according to claim 1 , wherein the first active layer comprises a group III nitride semiconductor material.
3. The semiconductor device according to claim 2 , wherein the first active layer comprises In x Al y Ga z N (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1).
4. The semiconductor device according to claim 2 , wherein the second active layer comprises a group III nitride semiconductor material, the second active layer having a wider band gap than the first active layer.
5. The semiconductor device according to claim 4 , wherein the second active layer comprises In x Al y Ga z N (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1).
6. The semiconductor device according to claim 1 , wherein the E-field management layer comprises In x Al y Ga z N (0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1).
7. The semiconductor device according to claim 1 , wherein the E-field management layer has a thickness about equal to or greater than 2 nm.
8. The semiconductor device according to claim 1 , wherein the E-field management layer comprises an intrinsic material or a material that includes therein impurities and/or defects that give rise to the resistivity.
9. The semiconductor device according to claim 1 wherein the E-field management layer includes impurities that are selected from the group consisting of Carbon, Iron, Magnesium and Zinc.
10. The semiconductor device according to claim 1 , wherein the E-field management layer includes impurities that have trap levels within a band gap of the E-field management layer or has defects.
11. The semiconductor device according to claim 1 , wherein the injection electrode and the E-field management layer establish a Schottky or ohmic contact therebetween.
12. The semiconductor device according to claim 1 , wherein the drain electrode and the E-field management layer establish a Schottky or ohmic contact therebetween.
13. The semiconductor device according to claim 1 , further comprising an insulator layer disposed over at least a portion of the E-field management layer, wherein at least a portion of the injection electrode is disposed over the insulator layer.
14. The semiconductor device according to claim 13 , wherein the insulator layer comprises at least one dielectric selected from the group consisting of Al 2 O 3 , Si x O y , Si x N y , Si x O y N z , Polytetrafluoroethylene, HfO 2 , AlN or a combination thereof.
15. The semiconductor device according to claim 13 , wherein the insulator layer has a dielectric constant below 200.
16. The semiconductor device according to claim 1 , further comprising a gate dielectric layer over which the gate electrode is disposed.
17. The semiconductor device according to claim 16 , wherein the gate dielectric layer comprises at least one dielectric selected from the group consisting of Al 2 O 3 , Si x O y , Si x N y , Si x O y N z , Polytetrafluoroethylene, HfO 2 , AlN or a combination thereof.
18. The semiconductor device according to claim 16 , wherein the gate dielectric layer has a dielectric constant below 200.
19. The semiconductor device according to claim 1 , wherein the E-field management layer comprises a semiconductor material.
20. The semiconductor device according to claim 1 , wherein the E-field management layer comprises a conductive oxide material.
21. A semiconductor device, comprising:
a substrate;
a first active layer disposed over the substrate;
a second active layer disposed on the first active layer such that a laterally extending conductive channel arises which extends in a lateral direction, the laterally extending conductive channel being located between the first active layer and the second active layer;
first and second electrodes electrically connected to the first active layer;
an E-field management layer for reducing electric-field gradients arising in the first and second active layers, the E-field management layer being disposed over the second active layer, wherein the E-field management layer includes impurities selected from the group consisting of Carbon, Iron, Magnesium and Zinc;
an injection electrode electrically connected to the E-field management layer;
wherein the first and second electrodes are source and drain electrodes, respectively, and further comprising a gate electrode disposed completely in a recess extending into the E-field management layer above an upper surface of the second active layer between the source electrode and the drain electrode,
wherein the injection electrode is disposed between the gate electrode and the drain electrode extending laterally towards the drain electrode without any electrical connection with either the source electrode, the drain electrode or the gate electrode.
22. The semiconductor device according to claim 1 wherein the gate electrode is disposed adjacent to the E-field management layer.