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Novel high gate barrier AlInAs/GaInAs/InP HEMT structure: Concept verification and key technologies
A novel high gate barrier (HGB) AlInAs/GaInAs/InP HEMT structure is proposed, which overcomes gate leakage current problems due to limited Schottky barrier height in common HEMT design. Gate leakage is a major contribution to low-frequency noise besides deep trap re-charging. The crucial point in the novel HEMT design is the insertion of an additional shallow p+- delta doped plane below the gate contact to enhance the effective barrier height. This work focusses on three important steps towards the realization of this structure, i.e. the verification of the barrier enhancing p+- delta doping concept, the validation of an accurate simulation of band structure and carrier distribution thoroughly tested by comparing predicted threshold voltages to values measured at fabricated devices, and the application of a highly selective gate recess technology. The introduced HEMT structure is expected to considerably improve the sensitivity of broadband high-speed receiver OEICs.