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Reliability of InAlAs/InGaAs HEMTs grown on GaAs substrate with metamorphic buffer
Zuverlässigkeit von InAlAs/InGaAs HEMTs auf GaAs Substrat mit metamorphem Buffer
The long term stability of 0.25 mu m InAlAs/InGaAs HEMTs grown on GaAs substrate with metamorphic buffer (MM-HEMT) was investigated by biased accelerated life tests in air and in nitrogen. By defining a 10 per cent-degradation failure criterion of transconductance we found a life time of 2x10(exp 7) h at T(ch)=125 deg 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 InPbased HEMTs.