Field-effect transistors whose gate electrodes are over semiconductor heterostructures and parts of source and drain electrodes

1. An apparatus, comprising:

a field-effect transistor comprising

a region of first inorganic semiconductor;

a layer of second inorganic semiconductor located on the region of the first inorganic semiconductor, the layer and region forming a semiconductor heterostructure;

source and drain electrodes being located in part on the layer; and

a gate electrode located to control a conductivity of a channel portion of the semiconductor heterostructure, the channel portion being located between the source and drain electrodes, the gate electrode being located vertically over the channel portion and being located over portions of the source and drain electrodes, the gate electrode and parts of the source and drain electrodes being located over a same side of the layer and being located over a same side of the region; and

wherein the transistor is capable of trapping a two-dimensional charge carrier gas in the channel portion of the semiconductor heterostructure.

2. The apparatus of claim 1 , wherein the field-effect transistor further comprises a dielectric layer located between the channel portion and the gate electrode and between the gate electrode and the portions of the source and drain electrodes.

3. The apparatus of claim 1 , wherein the first and second semiconductors include gallium and arsenic.

4. The apparatus of claim 3 , wherein one of the first semiconductor and the second semiconductor includes aluminum.

5. The apparatus of claim 4 , wherein the field-effect transistor further comprises a dielectric layer located between the channel portion and the gate electrode and between the gate electrode and the portions of the source and drain electrodes.

6. The apparatus of claim 4 , wherein the one of the first semiconductor and the second semiconductor has a ratio atoms of the aluminum to atoms of the gallium atoms, the ratio being x/(1-x), 0.1≦x≦0.25.

7. The apparatus of claim 1 , wherein the semiconductor heterostructure includes an Al x Ga (1-x) As/GaAs interface and the alloy parameter x satisfies 0<x<1.

8. The apparatus of claim 7 , wherein the alloy parameter x is in the range [0.05, 0.5].

9. An apparatus, comprising:

a field-effect transistor comprising:

a region of first inorganic semiconductor;

a layer of second inorganic semiconductor located on the region of the first inorganic semiconductor, the layer and region forming a semiconductor heterostructure;

source and drain electrodes being located in part on the layer; and

a gate electrode located to control a conductivity of a channel portion of the semiconductor heterostructure, the channel portion being located between the source and drain electrodes, the gate electrode being located vertically over the channel portion and being located over portions of the source and drain electrodes, the gate electrode and parts of the source and drain electrodes being located over a same side of the layer and being located over a same side of the region; and

wherein material of the source and drain electrodes is diffused into adjacent portions of the layer such that said material is diffused at least up to an interface between the layer and the region.

10. The apparatus of claim 9 , wherein the source and drain electrodes include a metal, the metal being diffused into the layer.

11. The apparatus of claim 9 , wherein the field-effect transistor further comprises a dielectric layer located between the channel portion and the gate electrode and between the gate electrode and the portions of the source and drain electrodes.

12. The apparatus of claim 9 , wherein the semiconductor heterostructure includes an Al x Ga (1-x) As/GaAs interface and the alloy parameter x satisfies 0<x<1.

13. The apparatus of claim 12 , wherein the alloy parameter x is in the range [0.05, 0.5].