In this thesis, the ternary compound semiconductor devices, i.e., AlInAs/GaInAs high electron mobility transistor (HEMT) and doped-channel field-effect transistor (DCFET) are analyzed and compared. The electron distribution DC and the high-frequency characteristics are depicted and demonstrated.
First, the AlInAs/GaInAs HEMT employs a delta-doped sheet inserted between AlInAs barrier layer and spacer layer, to from more carriers in the triangle quantum well and enables the two-dimensional electron gas (2DEG) to increase. Comparably, HEMT has better transconductance and high-frequency characteristics. However, it shows the poor device linearity. But, due to HEMT have parallel-conduction existence, which will introduce considerably large gate current, and lower gate turn-on voltage. In addition, due to the high channel resistance value, therefore the drain output current is small.
The channel of device AlInAs/GaInAs DCFET is uniformly doped. Although the high electron mobility is not so high the channel effective carrier concentration is big effectively. Its channel resistance is low, so it exhibits high drain output current. Furthermore, the gate is directly sitting on the undoped layer, and it shows larger gate turn-on voltage and broad gate swing. Significantly, not obvious gate leakage current is observed. Also, it shows good device linearity. But has the lower transconductance and high-frequency characteristics. Under simulated results, for the DCFET not parallel-conduction exists, and the gate is directly sitting on the undoped barrier layer. Thus, it has the better DC characteristics than the HEMT. However, for the HEMT due to the high 2DEG it shows large transconductance and the good high-frequency characteristics.