Reliability of InAlAs/InGaAs HEMTs grown on GaAs substrate with metamorphic buffer

The long term stability of 0.25 mu m InAlAs/InGaAs HEMTs grown on GaAs subs trate with metamorphic buffer (MM-HEMT) was investigated by biased accelera ted life tests in air and in nitrogen. By defining a 10%-degradation failur e criterion of transconductance we found a life time of 2x10(7) h at T-ch=1 25 degrees C and an activation energy of 1.8 eV in nitrogen atmosphere. The median life and the activation energy were found to be much smaller in air , which can be explained by passivation of the silicon donors with fluorine . The life time and the degradation of electrical parameters of MM HEMTs in air and nitrogen is comparable to InP-based HEMTs. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.