The effects of thermally stressing submicron InxGa1-xAs/InAlAs/InP (x ≥ 0.53) HEMTs for storage periods of up to 100 h at 200°C are discussed. DC characteristics are found to degrade. IDSS decreased from 299 mA/mm to 182 mA/mm. Gm decreased from 513 mS/mm to 209 mS/mm. Decreases in microwave performance were also measured. fT and fmax decreased by more than 30% and 20%, respectively. Evidence indicates that changes in the channel/buffer interface and layers manifested by the presence of additional trapping are responsible for this. Measurements of ohmic contacts show an increase from 0.19 Ω-mm to 0.26 Ω-mm. Results of X-ray analysis and Hall characterization are presented.
