| Summary: | 碩士 === 逢甲大學 === 電子工程所 === 95 === In the thesis, we intend to grow the δ-doped InxAl1-xAs/InyGa1-yAs/GaAs Metamorphic High Electron Mobility Transistor (MHEMTs) with InyGa1-yAs channel to effectively relieve the impact-ionization effects has been successfully fabricated by the molecular beam epitaxy (MBE) system. With the designs of an InGaAs channel layer and a larger energy bangap InAlAs Schottky contact layer, good carrier confinement, improved breakdown, low output conductance, and high voltage gain with good linearity have been simultaneously achieved.
However, the conversional pseudomorphic HEMTs (pHEMTs) exhibiting higher extrinsic transconductance, due to the impurity scattering effect will be eliminated in undoped InGaAs channel. In this work, we use the metamorphic buffer structure to grow the different indium content channel. Using a low “In” content channel, the breakdown voltage is enhanced due to the decrease in impact ionization effect. The low “In” content channel which has a better carrier confinement and the thermal stable due to large ΔEC between the Schottky contact and the channel layers. In addition, the high “In” content channel, because ΔEC small and the carrier confinement become poor, the high temperature characteristic of the device is also degraded.
The experimental results in low indium content channel shows good carrier confinement, thermal stability in high temperature, high breakdown voltage, large gate voltage swing and reduces the impact ionization effect. On the other hand, the high indium content channel shows high power performance, high extrinsic transconductance, high current density and high cut-off frequency applications. The temperature-dependent characteristics of InAlAs/InGaAs/GaAs metamorphic high electron mobility transistor have been studied in this work.
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