Performance of InAlGaAs/InGaAs HBTs with tunneling AlAs barrier layer

With the high speed demands on HBTs the base thickness is constantly being reduced making the base access etch one of the most challenging processing steps for industrial fabrication. In InAlGaAs/InGaAs HBTs an AlAs tunneling barrier layer can act as a selective etch stop layer. HBTs with a narrow base can then be processed using selective base access etch. The presence of a thin tunneling AlAs layer enhances the device performance without altering the offset voltage. HBTs with quaternary compounds and AlAs tunneling barriers show a significant reduction of the offset voltage, negative resistance effects and an improvement of the output conductance suggesting suitability for applications in integrated circuits and communication systems operating in microwave range frequencies.