QUALCOMM Incorporated
MULTI-GATE HIGH ELECTRON MOBILITY TRANSISTORS (HEMTs) EMPLOYING TUNED RECESS DEPTH GATES FOR IMPROVED DEVICE LINEARITY

Abstract:

A multi-gate HEMT includes at least two gates, with at least one recessed the same depth or at a deeper depth in a barrier layer than at least one other gate. Recessing a gate decreases the thickness of the barrier layer beneath the gate, reducing a density of high mobility carriers in a two-dimensional electron gas layer (2DEG) conductive channel formed at the heterojunction of a barrier layer and a buffer layer below the recessed gate. The recessed gate can increase gate control of the 2DEG conductive channel. The multi-gate HEMT has at least one gate recessed the same depth or a deeper depth into the buffer layer than another gate, which forms at least two different turn-on voltages for different gates. This can achieve improvement of transconductance linearity and a positive shift of the threshold voltage.