Enhancement mode gallium nitride power devices
Enhancement mode III-nitride devices are described. The 2DEG is depleted in the gate region so that the device is unable to conduct current when no bias is applied at the gate. Both gallium face and nitride face devices formed as enhancement mode devices.
1. An N-face enhancement mode high electrode mobility transistor device, comprising:
a substrate;
a heterostructure region and 2DEG region formed by a layer of AlGaN with a aluminum composition between 0 and 1 or equal to 1 and a GaN channel layer, wherein the heterostructure region is on the substrate and the GaN channel layer has a Ga-face adjacent to the layer of AlGaN; and
a cap in a recess of an N-face of the channel layer, wherein the cap does not overlie an access region of the device;
a gate formed on the cap; and
a source and drain on laterally opposing sides of the cap.
2. The device of claim 1 , wherein the cap is p-type Al z GaN.
3. The device of claim 2 , wherein the p-type Al z GaN is a graded layer where z changes gradually.
4. The device of claim 1 , wherein the cap comprises p-type Al z GaN and AlN layers.
5. The device of claim 1 , wherein the cap includes Al y GaN and Al x GaN, and the Al y GaN is closer to the gate than the Al x GaN is and y>x.
6. The device of claim 5 , wherein the Al y GaN and Al x GaN are doped p-type.
7. The device of claim 1 , wherein the cap includes Al y GaN and Al x GaN, the Al y GaN is closer to the gate than the Al x GaN is, Al y GaN and Al x GaN are doped p-type and x>y.
8. The device of claim 1 , wherein an access region between the gate and source and between the gate and drain is ion implanted.
9. The device of claim 8 , wherein the access region between the gate and source and between the gate and drain is ion implanted with n-type dopants.
10. The device of claim 1 , wherein an insulating layer is disposed between the gate and the cap.
11. The device of claim 10 , wherein the insulating layer comprises SiN x , SiO 2 , or AlN.
12. The device of claim 1 , further comprising a dielectric passivation layer over at least the access region.
13. The device of claim 12 , further comprising a field plate over the dielectric passivation layer.
14. The device of claim 13 , wherein the field plate is a slant field plate.
15. The device of claim 1 , further comprising a GaN buffer layer between the substrate and the heterostructure region.
16. The device of claim 1 , wherein a thickness of the GaN channel layer below the gate is about 5 nm.
17. The device of claim 1 , wherein the thickness of the GaN channel layer below the gate is about 5 nm.
18. The device of claim 1 , further comprising an AlN interlayer between the GaN channel layer and the layer of AlGaN.
19. The device of claim 1 , wherein the device is capable of blocking at least 600V.
20. The device of claim 1 , wherein an internal barrier of the device is at least 1.5 eV.