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 N₂ 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_0.7Ga_0.3Sb-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 2times10⁶ 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.