Oxide heterostructures having spatially separated electron-hole bilayers
Oxide heterostructures that form spatially separated electron-hole bilayers are provided. Also provided are electronic devices that incorporate the oxide heterostructures. The oxide heterostructure includes a base layer of SrTiO 3 , a polar layer of LaAlO 2 , and a non-polar layer of SrTiO 3 . Within the oxide heterostructures, a two-dimensional hole gas (2DHG) is formed at the interface between the non-polar layer and the polar layer and a two-dimensional electron gas (2DEG) is formed at the interface between the polar layer and the base layer.
1. An oxide heterostructure comprising:
a base layer comprising SrTiO 3 ;
a polar layer comprising LaAlO 3 on the base layer;
a non-polar layer comprising SrTiO 3 on the polar layer, the SrTiO 3 of the non-polar layer having a lower oxygen vacancy concentration than the SrTiO 3 of the base layer,
a two-dimensional electron gas confined at an interface between the base layer and the polar layer; and
a two-dimensional hole gas confined at an interface between the polar layer and the non-polar layer, wherein the two-dimensional hole gas has a Hall hole mobility that is at least as high as the Hall electron mobility of the two-dimensional electron gas at a temperature in the range from 1 K to 50 K.
2. The heterostructure of claim 1 , wherein the SrTiO 3 of the non-polar layer has an oxygen vacancy index of no greater than 2.
3. An oxide heterostructure comprising:
a base layer comprising SrTiO 3 ;
a polar layer comprising LaAlO 3 on the base layer;
a non-polar layer comprising SrTiO 3 on the polar layer, the SrTiO 3 of the non-polar layer having a lower oxygen vacancy concentration than the SrTiO 3 of the base layer,
a two-dimensional electron gas confined at an interface between the base layer and the polar layer; and
a two-dimensional hole gas confined at an interface between the polar layer and the non-polar layer, wherein the two-dimensional hole gas has a Hall hole mobility of at least 4×10 2 cm 2 V −1 s −1 at a temperature of 20 K.
4. The heterostructure of claim 1 , wherein the polar layer has a thickness of at least 5 unit cells.
5. The heterostructure of claim 2 , wherein the polar layer has a thickness of at least 5 unit cells.
6. A transistor comprising:
the oxide heterostructure of claim 1 ;
a source electrode;
a drain electrode, wherein the source electrode and the drain electrode are in electrical communication through either the 2DEG or the 2DHG; and
a gate electrode that is configured to alter the current flowing between the source electrode and the gate electrode when a gate voltage is applied to the gate electrode.
7. The heterostructure of claim 1 , wherein the polar layer has a thickness of at least 4 unit cells.
8. The heterostructure of claim 3 , wherein the two-dimensional hole gas has a Hall hole mobility of at least 5×10 2 cm 2 V −1 s −1 s at a temperature in the range from 1 K to 10 K.
9. The heterostructure of claim 3 , wherein the SrTiO 3 of the non-polar layer has an oxygen vacancy index of no greater than 2.
10. The heterostructure of claim 3 , wherein the polar layer has a thickness of at least 5 unit cells.
11. The heterostructure of claim 10 , wherein the polar layer has a thickness of at least 5 unit cells.