Degradation mechanisms of 0.1 μm AlSb/InAs HEMTS for ultralow-power applications

The degradation mechanisms of 0.1 mum AlSb/InAs HEMTs subjected to elevated-temperature lifetesting at three temperatures in N
₂
atmosphere were investigated. Device degradation exhibits the increase of non-pinch-off drain current (I
_DS
), the decrease of transconductance (g
_m
) and the gate current (I
_G
) increase. The I
_G
increase was found to correlate with material degradation on the gate-recess and Al
_0.7
Ga
_0.3
Sb-mesa-floor surfaces. Higher oxygen content was detected on these surfaces, indicating that they were modified by oxidation, which resulted in the I
_G
increase. Despite the degradation observed in 0.1 mum AlSb/InAs HEMTs, the three-temperature lifetesting shows that the activation energy (E
_a
) is approximately 1.5 eV and demonstrates a median time to failure (MTF)of 2times10
⁶
hours at T
_junction
of 85degC. This reliability result is essential for successful insertion of AlSb/InAs HEMTs into systems with ultralow-power requirements. Moreover, ohmic-metal lateral diffusion of Pd and Au elements was observed. To avoid potential ohmic-metal-lateral-diffusion induced device failure, lifetesting temperatures were kept below 190degC in this investigation.