Low-Noise Bias Reliability of AlInAs/GaInAs Modulation-Doped Field Effect Transistors with Linearly Graded Low-Temperature Buffer Layers Grown on GaAs Substrates

The low-noise bias reliability of 0.1 µm T-gate Al0.48In0.52As/Ga0.47In0.53As modulation-doped field effect transistors (MODFETs), grown on GaAs was investigated. Al0.48In0.52As/Ga0.47In0.53As MODFETs were grown on mismatched GaAs substrates by the insertion of a compositionally linearly-graded low-temperature buffer (LGLTB) layer. Transmission electon microscopy (TEM) analysis of the layers indicates that the majority of the defects are confined to the buffer layer. Although the LGLTB layer is highly defective, there is no indication that the low-bias reliability of these devices is compromised. MODFETs with a LGLTB layer show reliability under high temperature operating life (HTOL) tests at a drain bias of 1 V and 200 mA/mm, comparable to reported MODFETs grown lattice-matched to InP. The extrapolated mean-time-to-failure (MTTF), based on the drift of the zero-gate bias current, Idss, at temperatures of 200 to 240°C, exceeds 106 h at a channel temperature of 125°C. The drift in Idss arises primarily from a positive shift in threshold voltage. The low-bias Rd degradation behavior of these devices is also similar to devices grown on InP.