Carbon doped GaAsSb
The process was developed by EpiWorks with source materials coming from UK company Epichem and InP substrates from InPact. The project goal was to obtain a carbon-doped GaAsSb majority carrier mobility greater than 40 cm2/V/sec for a doping level greater than 7E19/cm3. This was achieved. Carbon doping levels above 8E19/cm3 were also demonstrated.
Quesnell Hartmann, president of EpiWorks, reports: "We are very excited about the results and have already begun applying the material in a heterojunction bipolar transistor (HBT). GaAsSb HBTs are an important potential technology for high-speed digital and military applications and could be a breakthrough technology in high-speed wireless applications. By developing the process on full 75mm wafers, we have shown that the uniformity of GaAsSb is comparable to c-doped InGaAs, which is critical for HBTs."
The process was developed in a production style metal-organic chemical vapour deposition (MOCVD) system, capable of producing eight 75mm wafers, or eight 100mm wafers in a single production run. The single layer non-uniformity was less than 2% across the wafer as measured by the contactless resistivity measurement method.