High-temperature threshold characteristics of a symmetrically graded InAlAs/ InxGa1−xAs/GaAs metamorphic high electron mobility transistor

High-temperature threshold characteristics of a symmetrically graded -doped InAlAs/ InxGa1−xAs/GaAs x=0.5→0.65→0.5 metamorphic high electron mobility transistor MHEMT have been investigated. The thermal threshold coefficients, defined as Vth / T, are superiorly low at 0.9 mV/K from 300 to 420 K and at −0.75 mV/K from 420 to 500 K. An interesting polarity change of the thermal threshold coefficient was observed around 420 K due to the variation of thermal modulation effects. The present MHEMT device, with stabilized thermal threshold variations and superior high-temperature linearity characteristics, is promising for high-temperature circuit applications. © 2006 American Institute of Physics. DOI: 10.1063/1.2208926