Group III nitride-based radio frequency amplifiers having back side source, gate and/or drain terminals

1. A radio frequency (“RF”) amplifier, comprising:

a Group III nitride-based RF amplifier die that includes a semiconductor layer structure and a gate terminal, a source terminal and a drain terminal on the semiconductor layer structure,

wherein a plurality of unit cell transistors are provided in an upper portion of the semiconductor layer structure, and at least two of the gate terminal, the drain terminal and the source terminal are provided on a lower surface of the semiconductor layer structure,

wherein at least one of the gate terminal and the drain terminal is electrically connected to the unit cell transistors through a conductive via, and

wherein an inductance of the conductive via comprises at least a portion of a matching circuit.

2. The RF amplifier of claim 1 , wherein the semiconductor layer structure comprises a growth substrate, a channel layer and a barrier layer, where the channel layer is between the growth substrate and the barrier layer.

3. The RF amplifier of claim 2 , wherein the Group III nitride-based RF amplifier die further includes a metallization structure that comprises a plurality of gate fingers, a plurality of drain fingers and a plurality of source fingers that are on barrier layer opposite the channel layer, and

wherein the gate fingers are electrically connected to the gate terminal via the one or more conductive gate vias, and the drain fingers are electrically connected to the drain terminal via the one or more conductive drain vias.

4. The RF amplifier of claim 3 , wherein the one or more conductive gate vias and the one or more conductive drain vias extend through the growth substrate.

5. The RF amplifier of claim 1 , further comprising an interconnection structure that includes a gate pad that is electrically connected to the gate terminal, a drain pad that is electrically connected to the drain terminal and a source pad that is electrically connected to the source terminal.

6. The RF amplifier of claim 5 , wherein the gate pad, the drain pad and the source pad are electrically connected to the gate terminal, the drain terminal and the source terminal, respectively, via a conductive epoxy pattern.

7. The RF amplifier of claim 5 , wherein the gate terminal overlaps the gate pad along a first axis that is perpendicular to an upper surface of the interconnection structure, the drain terminal overlaps the drain pad along a second axis that is perpendicular to an upper surface of the interconnection structure, and the source terminal overlaps the source pad along a third axis that is perpendicular to an upper surface of the interconnection structure.

8. The RF amplifier of claim 1 , wherein the one or more conductive gate vias, the one or more conductive drain vias and the one or more conductive source vias all have substantially a same shape and substantially a same cross-sectional area.

9. The RF amplifier of claim 5 , wherein the interconnection structure includes at least a first portion of the matching circuit and the conductive via comprises a second portion of the matching circuit.

10. A radio frequency (“RF”) amplifier, comprising:

a Group III nitride-based RF amplifier die that includes:

a semiconductor layer structure that includes a channel layer and a barrier layer on the channel layer;

a gate terminal;

a drain terminal;

a source terminal;

a plurality of gate fingers that are electrically connected to the gate terminal via at least one conductive gate via;

a plurality of drain fingers that are electrically connected to the drain terminal via at least one conductive drain via; and

a plurality of source fingers that are electrically connected to the source terminal via at least one conductive source via;

wherein the gate fingers, the drain fingers and the source fingers are all on a first side of the semiconductor layer structure,

wherein the gate terminal, the drain terminal and the source terminal are all on a second side of the semiconductor layer structure that is opposite the first side, and

wherein at least one of a number, a size and a shape of at least one of the conductive gate vias, the conductive drain vias and the conductive source vias is configured to optimize at least one of impedance matching and heat dissipation in the RF amplifier.

11. The RF amplifier of claim 10 , wherein the semiconductor layer structure further comprises a growth substrate, and the channel layer is between the growth substrate and the barrier layer.

12. The RF amplifier of claim 11 , wherein the at least one conductive gate via and the at least one conductive drain via extend completely through the growth substrate.

13. The RF amplifier of claim 12 , wherein the at least one conductive gate via and the at least one conductive drain via each comprise metal-plated vias that extend completely through the semiconductor layer structure.

14. The RF amplifier of claim 10 , further comprising an interconnection structure that includes a gate pad that is electrically connected to the gate terminal, a drain pad that is electrically connected to the drain terminal and a source pad that is electrically connected to the source terminal.

15. The RF amplifier of claim 14 , wherein the gate terminal overlaps the gate pad along a first axis that is perpendicular to an upper surface of the interconnection structure, the drain terminal overlaps the drain pad along a second axis that is perpendicular to an upper surface of the interconnection structure, and the source terminal overlaps the source pad along a third axis that is perpendicular to an upper surface of the interconnection structure.

16. A Group III nitride-based radio frequency (“RF”) amplifier die, comprising:

a semiconductor layer structure that has a top side and a bottom side that is opposite the top side;

a plurality of gate fingers on the top side of the semiconductor layer structure;

a plurality of source fingers on the top side of the semiconductor layer structure;

a plurality of drain fingers on the top side of the semiconductor layer structure; and

a gate terminal, a drain terminal and a source terminal, at least two of which are on the bottom side of the semiconductor layer structure,

wherein the gate terminal is electrically connected to the plurality of gate fingers via one or more conductive gate vias, the drain terminal is electrically connected to the plurality of drain fingers via one or more conductive drain vias, and the source terminal is electrically connected to the plurality of source fingers via one or more conductive source vias, and

wherein at least one of the one or more conductive gate vias and the one or more conductive drain vias is offset from the one or more conductive source vias.

17. The Group III nitride-based RF amplifier die of claim 16 , wherein the semiconductor layer structure comprises a growth substrate, a channel layer and a barrier layer, where the channel layer is between the growth substrate and the barrier layer, and

wherein the one or more conductive gate vias, the one or more conductive drain vias and the one or more conductive source vias extend completely through the growth substrate.

18. The RF amplifier of claim 1 , wherein the matching circuit comprises at least one of an impedance matching circuit and a harmonic termination circuit.

19. The RF amplifier of claim 1 , wherein the gate terminal is electrically connected to the unit cell transistors through one or more conductive gate vias, the drain terminal is electrically connected to the unit cell transistors through one or more conductive drain vias, and the source terminal is electrically connected to the unit cell transistors through one or more conductive source vias, and wherein at least one of the conductive gate vias and the conductive drain vias are offset from the conductive source vias.

20. The Group III nitride-based RF amplifier die of claim 16 , wherein an inductance of at least one of the one or more conductive gate vias and the one or more conductive drain vias comprises at least a portion of a matching circuit.