A method of fabricating an Enhancement mode Heterojunction Field Effect Transistor (HFET) device, the method comprising: receiving a device substantially comprising a depletion mode HFET wherein a barrier layer and channel layer of the HFET comprise Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) respectively; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of:; a) forming oxidized AlGaN in the gate region of the barrier layer-in the depletion mode HFET with Oxygen (02)_plasma for a first time; then b) etching the oxidized AlGaN in the depletion mode HFET with Boron Tile-ide Trichloride (BC l3) for a second time.

A method of fabricating an Enhancement mode HFET device, the method comprising: receiving a device substantially comprising a depletion mode HFET; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of thinning a gate region in increments of 1.2 to 2.5 nanometers.

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A method of fabricating an enhancement mode semiconductor active device, comprising the steps of: a) receiving a vertically inhomogeneous I II -Nitride semiconductor structure comprising a barrier layer disposed on a channel layer and wherein the channel layer exhibits a two-dimensional electron gas; b) introducing oxygen (0 2) plasma into an exposed region of the barrier layer to form an oxide layer; c) introducing boron trichloride (BC l3)_ plasma into the exposed region to etch the formed oxide layer; d) repeating steps b and c to cause the channel layer to be depleted of charge carriers in the exposed region; e) completing the formation of the said active device through the formation of source, drain and gate contacts; -3- wherein the said action (d) causes the said active device to have a positive threshold voltage.

A method of fabricating an Enhancement mode Heterojunction Field Effect Transistor (HFET) device, the method comprising: receiving a device substantially comprising a depletion mode HFET wherein a barrier layer and channel layer of the HFET comprise Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) respectively; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of:; a) forming oxidized AlGaN in the gate region of the barrier layer-in the depletion mode HFET with Oxygen (02)_plasma for a first time; then b) etching the oxidized AlGaN in the depletion mode HFET with Boron Tile-ide Trichloride (BC l3) for a second time.

A method of fabricating an Enhancement mode HFET device, the method comprising: receiving a device substantially comprising a depletion mode HFET; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of thinning a gate region in increments of 1.2 to 2.5 nanometers.

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A method of fabricating an enhancement mode semiconductor active device, comprising the steps of: a) receiving a vertically inhomogeneous I II -Nitride semiconductor structure comprising a barrier layer disposed on a channel layer and wherein the channel layer exhibits a two-dimensional electron gas; b) introducing oxygen (0 2) plasma into an exposed region of the barrier layer to form an oxide layer; c) introducing boron trichloride (BC l3)_ plasma into the exposed region to etch the formed oxide layer; d) repeating steps b and c to cause the channel layer to be depleted of charge carriers in the exposed region; e) completing the formation of the said active device through the formation of source, drain and gate contacts; -3- wherein the said action (d) causes the said active device to have a positive threshold voltage.

A method of fabricating an Enhancement mode Heterojunction Field Effect Transistor (HFET) device, the method comprising: receiving a device substantially comprising a depletion mode HFET wherein a barrier layer and channel layer of the HFET comprise Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) respectively; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of:; a) forming oxidized AlGaN in the gate region of the barrier layer-in the depletion mode HFET with Oxygen (02)_plasma for a first time; then b) etching the oxidized AlGaN in the depletion mode HFET with Boron Tile-ide Trichloride (BC l3) for a second time.

A method of fabricating an Enhancement mode HFET device, the method comprising: receiving a device substantially comprising a depletion mode HFET; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of thinning a gate region in increments of 1.2 to 2.5 nanometers.

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A method of fabricating an enhancement mode semiconductor active device, comprising the steps of: a) receiving a vertically inhomogeneous I II -Nitride semiconductor structure comprising a barrier layer disposed on a channel layer and wherein the channel layer exhibits a two-dimensional electron gas; b) introducing oxygen (0 2) plasma into an exposed region of the barrier layer to form an oxide layer; c) introducing boron trichloride (BC l3)_ plasma into the exposed region to etch the formed oxide layer; d) repeating steps b and c to cause the channel layer to be depleted of charge carriers in the exposed region; e) completing the formation of the said active device through the formation of source, drain and gate contacts; -3- wherein the said action (d) causes the said active device to have a positive threshold voltage.

A method of fabricating an Enhancement mode Heterojunction Field Effect Transistor (HFET) device, the method comprising: receiving a device substantially comprising a depletion mode HFET wherein a barrier layer and channel layer of the HFET comprise Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) respectively; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of:; a) forming oxidized AlGaN in the gate region of the barrier layer-in the depletion mode HFET with Oxygen (02)_plasma for a first time; then b) etching the oxidized AlGaN in the depletion mode HFET with Boron Tile-ide Trichloride (BC l3) for a second time.

A method of fabricating an Enhancement mode HFET device, the method comprising: receiving a device substantially comprising a depletion mode HFET; forming an enhancement mode gate region in the depletion mode HFET by repeated cycles of thinning a gate region in increments of 1.2 to 2.5 nanometers.

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A method of fabricating an enhancement mode semiconductor active device, comprising the steps of: a) receiving a vertically inhomogeneous I II -Nitride semiconductor structure comprising a barrier layer disposed on a channel layer and wherein the channel layer exhibits a two-dimensional electron gas; b) introducing oxygen (0 2) plasma into an exposed region of the barrier layer to form an oxide layer; c) introducing boron trichloride (BC l3)_ plasma into the exposed region to etch the formed oxide layer; d) repeating steps b and c to cause the channel layer to be depleted of charge carriers in the exposed region; e) completing the formation of the said active device through the formation of source, drain and gate contacts; -3- wherein the said action (d) causes the said active device to have a positive threshold voltage.