Frequency-dependent characteristics and trap studies of lattice-matched (x=0.53) and strained (x>0.53) In 0.52Al0.48As/Inx Ga1-xAs HEMTs

The low-frequency characteristics of InAlAs/In_xGa_1-xAs high-electron-mobility transistors (HEMTs) are studied, and trap densities are evaluated. The HEMTs´ transductance (g_m) and output resistance (R_ds) dispersion are smallest for 60% indium (In) content and largest for 53% In. The maximum dispersion for the 53% In sample is ~6% for g_m and ~13.3% for R_ds corresponding to lower values than observed in MESFETs. The R_ds dispersion characteristics are weaker than in AlGaAs/GaAs HEMTs and manifest themselves primarily up to 100 kHz. An analysis of the dispersion results indicates that, unlike in the case of MESFETs, the channel region under the gate rather than the access regions is responsible for the dispersion. Interface state densities were extracted by the AC conductance method and were found to follow the same trend as the g_m and R_ds dispersion: maximum values (2.69×10¹² cm^-2/eV^-1) for 53% In and minimum (1.98×10¹² cm^-2/eV^-1) for 60% In