Hydrogen Degradation of InP HEMTs and GaAs PHEMTs

Jesus A. del ALAMO  Roxann R. BLANCHARD  Samuel D. MERTENS  

IEICE TRANSACTIONS on Electronics   Vol.E84-C   No.10   pp.1289-1293
Publication Date: 2001/10/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Joint Special Issue on Heterostructure Microelectronics with TWHM 2000 (Topical Workshop on Heterostructure Microelectronics 2000))
Category: Hetero-FETs & Their Integrated Circuits
high-electron mobility transistor,  hydrogen,  reliability,  InP,  GaAs,  

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We have carried out a systematic study of the impact of hydrogen exposure on InP HEMTs and GaAs PHEMTs with Ti/Pt/Au gates. Hydrogen poisoning is an important reliability concern in these devices. Our work has provided ample evidence supporting the formation of TiH inside the gate structure upon exposure of HEMTs to a hydrogen environment. The resulting volume expansion of the gate stresses the semiconductor heterostructure underneath and, through the piezoelectric effect, results in a shift of the threshold voltage of the device. This mechanism is largely reversible. Independently of this, we have found that H2 upsets the stoichiometry of the exposed InAlAs barrier in the recessed region right next to the gate. This irreversebly changes the extrinsic sheet carrier concentration in the channel and affects other figures of merit such as the breakdown voltage. This understanding should be instrumental in identifying device-level solutions to this problem.