Quantum dot devices with modulation doped stacks
Disclosed herein are quantum dot devices, as well as related computing devices and methods. For example, in some embodiments, a quantum dot device may include: a quantum well stack including a quantum well layer, a doped layer, and a barrier layer disposed between the doped layer and the quantum well layer; and gates disposed above the quantum well stack. The doped layer may include a first material and a dopant, the first material may have a first diffusivity of the dopant, the barrier layer may include a second material having a second diffusivity of the dopant, and the second diffusivity may be less than the first diffusivity.
1. A quantum dot device, comprising:
a quantum well stack including a quantum well layer, a doped layer, and a barrier layer between the doped layer and the quantum well layer, wherein the doped layer includes a first material and a dopant, the first material has a first diffusivity of the dopant, the barrier layer includes a second material having a second diffusivity of the dopant, and the second diffusivity is less than the first diffusivity; and
gates above the quantum well stack;
wherein the first material includes silicon and germanium, the second material includes silicon and germanium, the first material has a first germanium content, the second material has a second germanium content, and the first germanium content is different from the second germanium content.
2. The quantum dot device of claim 1 , wherein the doped layer is a first doped layer, the quantum well stack further includes a second doped layer, and the barrier layer is between the first doped layer and the second doped layer.
3. The quantum dot device of claim 2 , wherein the second doped layer includes the first material and the dopant.
4. The quantum dot device of claim 3 , wherein the second doped layer is between the barrier layer and the quantum well layer, and the first and second doped layers have equal concentrations of the dopant.
5. The quantum dot device of claim 3 , wherein the second doped layer is between the barrier layer and the quantum well layer, the first doped layer has a first concentration of the dopant, the second doped layer has a second concentration of the dopant, and the second concentration of the dopant is less than the first concentration of the dopant.
6. The quantum dot device of claim 2 , wherein the barrier layer is a first barrier layer, the quantum well stack further includes a second barrier layer, and the second barrier layer is between the second doped layer and the quantum well stack.
7. The quantum dot device of claim 6 , wherein the second barrier layer includes the second material.
8. The quantum dot device of claim 6 , wherein the quantum well stack further includes a third doped layer between the second barrier layer and the quantum well stack.
9. The quantum dot device of claim 8 , wherein the third doped layer includes the first material and the dopant.
10. The quantum dot device of claim 9 , wherein the second doped layer is between the barrier layer and the quantum well layer, the first doped layer has a first concentration of the dopant, the second doped layer has a second concentration of the dopant, the third doped layer has a third concentration of the dopant, the second concentration of the dopant is less than the first concentration of the dopant, and the third concentration of the dopant is less than the second concentration of the dopant.
11. The quantum dot device of claim 9 , wherein the quantum well stack further includes a third barrier layer between the third doped layer and the quantum well stack.
12. The quantum dot device of claim 1 , wherein the doped layer is between the gates and the quantum well layer.
13. The quantum dot device of claim 1 , wherein the quantum well layer is between the gates and the doped layer.
14. A quantum computing device, comprising:
a quantum processing device, wherein the quantum processing device includes a first quantum well stack region and a second quantum well stack region, an active quantum well layer in the first quantum well stack region, a read quantum well layer in the second quantum well stack region, a doped layer in the first quantum well stack region spaced away from the active quantum well layer by a barrier layer, the doped layer includes a first material and a dopant, the first material has a first diffusivity of the dopant, the barrier layer includes a second material having a second diffusivity of the dopant, and the second diffusivity is less than the first diffusivity;
a non-quantum processing device, coupled to the quantum processing device, to control voltages applied to gates on the first and second quantum well stack regions; and
a memory device to store data generated by the read quantum well layer during operation of the quantum processing device;
wherein the first material includes silicon and germanium, the second material includes silicon and germanium, the first material has a first germanium content, the second material has a second germanium content, and the first germanium content is different from the second germanium content.
15. The quantum computing device of claim 14 , wherein the doped layer and the active quantum well layer are coupled by a conductive pathway through the barrier layer.
16. A quantum dot device, comprising:
a quantum well stack including a quantum well layer, a first doped layer, a second doped layer, and a barrier layer between the first doped layer and the quantum well layer, wherein the first doped layer includes a first material and a dopant, the first material has a first diffusivity of the dopant, the barrier layer includes a second material having a second diffusivity of the dopant, the second diffusivity is less than the first diffusivity, and the barrier layer is between the first doped layer and the second doped layer; and
gates above the quantum well stack;
wherein the first material includes silicon or germanium or a combination thereof, and the second material includes silicon or germanium or a combination thereof, a III-V material, or silicon and carbon.
17. The quantum dot device of claim 16 , wherein the second material includes a III-V material.
18. The quantum dot device of claim 16 , wherein the second material includes intrinsic silicon.
19. The quantum dot device of claim 16 , wherein the second doped layer includes the first material and the dopant.
20. The quantum dot device of claim 19 , wherein the second doped layer is between the barrier layer and the quantum well layer, and the first and second doped layers have equal concentrations of the dopant.
21. The quantum dot device of claim 19 , wherein the second doped layer is between the barrier layer and the quantum well layer, the first doped layer has a first concentration of the dopant, the second doped layer has a second concentration of the dopant, and the second concentration of the dopant is less than the first concentration of the dopant.
22. The quantum dot device of claim 16 , wherein the barrier layer is a first barrier layer, the quantum well stack further includes a second barrier layer, and the second barrier layer is between the second doped layer and the quantum well stack.
23. The quantum dot device of claim 22 , wherein the second barrier layer includes the second material.
24. A quantum computing device, comprising:
a quantum processing device, wherein the quantum processing device includes a first quantum well stack region and a second quantum well stack region, an active quantum well layer in the first quantum well stack region, a read quantum well layer in the second quantum well stack region, a first doped layer in the first quantum well stack region spaced away from the active quantum well layer by a barrier layer, a second doped layer in the first quantum well stack region, the first doped layer includes a first material and a dopant, the first material has a first diffusivity of the dopant, the barrier layer includes a second material having a second diffusivity of the dopant, the second diffusivity is less than the first diffusivity, the barrier layer is between the first doped layer and the second doped layer, the first material includes silicon or germanium or a combination thereof, and the second material includes silicon or germanium or a combination thereof, a III-V material, or silicon and carbon;
a non-quantum processing device, coupled to the quantum processing device, to control voltages applied to gates on the first and second quantum well stack regions; and
a memory device to store data generated by the read quantum well layer during operation of the quantum processing device.
25. The quantum computing device of claim 24 , wherein the first doped layer and the active quantum well layer are coupled by a conductive pathway through the barrier layer.