Shifting the pinch-off voltage of an InP high electron mobility transistor with a metal ring

A high electron mobility transistor (HEMT) device comprising:

• a substrate;
• a plurality of semiconductor layers provided on the substrate, said plurality of semiconductor layers including a buffer layer;
• at least one contact layer provided on the semiconductor layers;
• a source terminal and a drain terminal formed on the at least one contact layer;
• at least one gate terminal formed on one of the plurality of semiconductor layers other than the buffer layer;
• and
• a metal ring formed on the buffer layer at a location so that the source terminal, the drain terminal and the at least one gate terminal are within an outer circumference defined by the metal ring, wherein the metal ring includes an ohmic portion and an electrode portion, said metal ring operating to shift a pinch-off voltage of the device.

A high electron mobility transistor (HEMT) device comprising:

• an InP substrate;
• a plurality of semiconductor layers provided on the substrate including an InAlAs buffer layer formed on the substrate, an InGaAs channel layer formed on the buffer layer, an InAlAs spacer layer formed on the channel layer, an InAlAs barrier layer formed on the spacer layer, an InAlAs contact layer formed on the barrier layer, and an InGaAs contact layer formed on the InAlAs contact layer, wherein the spacer layer, the barrier layer and the contact layers define a mesa;
• a source terminal, a drain terminal and at least one gate terminal formed on the mesa;
• and
• a closed metal ring formed on the buffer layer and around the mesa, wherein the metal ring includes an ohmic portion and an electrode portion, said metal ring operating to shift a pinch-off voltage of the device.