Three dimensional vertically structured electronic devices

1. An apparatus, comprising:

at least one vertical transistor, comprising:

a substrate comprising a first semiconductor material;

at least one three dimensional (3D) structure above the substrate, wherein the 3D structure comprises the first semiconductor material;

a heterojunction capping layer above an upper surface of the 3D structure, the heterojunction capping layer comprising a second semiconductor material, wherein the first and second semiconductor materials have a different bandgap;

a source region positioned below the heterojunction capping layer; and

a passivation layer extending along a portion of at least one vertical sidewall of the 3D structure, wherein a total height of the passivation layer is in a range of greater than 0% to less than 100% of the total height of the 3D structure,

wherein the source region is positioned entirely above the passivation layer.

2. The apparatus as recited in claim 1 , wherein the first semiconductor material comprises GaN, and wherein the second semiconductor material comprises at least one of: Al x Ga 1-x N, wherein 0≤x≤1; In y Ga 1-y N, wherein 0≤y≤1; B z Ga 1-z N, wherein 0≤z≤1; and TlGaN.

3. The apparatus as recited in claim 1 , wherein the vertical transistor comprises:

the source region positioned above the passivation layer and coupled to the portion of at least one vertical sidewall of the 3D structure;

a gate region coupled to an upper surface of the heterojunction capping layer; and

a drain region coupled to a lower surface of the substrate.

4. The apparatus as recited in claim 1 , wherein the passivation layer comprises at least one of: SiN x , SiO 2 , TiO 2 , ZnO, BN, B, Al 2 O 3 , Ga 2 O 3 , MgO, Y 2 O 3 , and Gd 2 O 3 .

5. The apparatus as recited in claim 1 , wherein an upper surface of the source region lies along the same plane as a lower surface of the heterojunction capping layer.

6. The apparatus as recited in claim 3 , wherein the gate region is positioned entirely above the upper surface of the heterojunction capping layer.

7. The apparatus as recited in claim 3 , wherein the drain region is below the substrate.

8. The apparatus as recited in claim 3 , wherein the source region extends along the at least one vertical sidewall of the 3D structure.

9. The apparatus as recited in claim 1 , wherein the source region surrounds a periphery of the 3D structure.

10. A method of forming the vertical transistor as recited in claim 1 , the method comprising:

forming a layer of a first region comprising the first semiconductor material above the substrate;

defining three dimensional (3D) structures in the layer;

forming a second region in at least one vertical sidewall of each 3D structure;

forming the heterojunction capping layer above the upper surface of each 3D structure;

forming the source region entirely above the passivation layer; and

forming an isolation region between the 3D structures.

11. The method as recited in claim 1 , wherein the 3D structures are defined via at least one technique selected from a group of techniques consisting of: an etching technique and an ion implantation technique.

12. The method as recited in claim 1 , wherein each 3D structure comprises the first region having a first conductivity type and the second region having a second conductivity type, the second region including a portion of at least one vertical sidewall of the 3D structure, wherein the isolation region is positioned between the 3D structures.

13. An apparatus, comprising:

at least one vertical transistor, comprising:

a substrate comprising a first semiconductor material;

at least one three dimensional (3D) structure above the substrate, wherein the 3D structure comprises the first semiconductor material;

a heterojunction capping layer above an upper surface of the 3D structure, the heterojunction capping layer comprising a second semiconductor material, wherein the first and second semiconductor materials have a different bandgap;

a source region positioned below the heterojunction capping layer;

a passivation layer extending along a portion of at least one vertical sidewall of the 3D structure, wherein a total height of the passivation layer is in a range of greater than 0% to less than 100% of the total height of the 3D structure,

wherein the source region is positioned above the passivation layer and coupled to a portion of at least one vertical sidewall of the 3D structure;

a gate region coupled to an upper surface of the heterojunction capping layer; and

a drain region coupled to a lower surface of the substrate,

wherein the gate region is positioned entirely above the 3D structure.

14. An apparatus, comprising:

at least one vertical transistor, comprising:

a substrate comprising a first semiconductor material;

at least one three dimensional (3D) structure above the substrate, wherein the 3D structure comprises the first semiconductor material, wherein the substrate and 3D structure have the same conductivity type;

a heterojunction capping layer above an upper surface of the 3D structure, the heterojunction capping layer comprising a second semiconductor material;

a source region positioned entirely below the heterojunction capping layer;

a gate region coupled to an upper surface of the heterojunction capping layer;

a passivation layer positioned on at least one vertical sidewall of the 3D structure, wherein the source region is positioned above the passivation layer and extends along the at least one vertical sidewall of the 3D structure; and

a drain region coupled to a lower surface of the substrate.

15. The apparatus as recited in claim 14 , wherein an upper surface of the source region lies along the same plane as a lower surface of the heterojunction capping layer.