Enhanced Reliability of Radiation-hardened III-V Semiconductor-based Field Effect Transistors Using C-doped Low-temperature Buffer

Low-temperature MBE grown GaAs (LT-GaAs) contains a high concentration of excess As which gives rise to ultra-fast carrier-trapping time and excellent radiation hardness. In as-grown layers most of this excess As is in the form of As(Ga) antisite defects, of which only ~1% are ionized. Thermal annealing upon overgrowth with a device structure or during device processing results in a decrease of the As(Ga) concentration by about a factor of 100, accompanied by out-diffusion of excess As into adjacent layers. The benefits of LT-GaAs buffer layers for device isolation and increased radiation hardness can thus be realized only if their stability can be improved. Doping the LT-GaAs layers with Be (LT-GaAs:Be) can thermally-stabilize As(Ga) antisite defects and increases their incorporation. However, Be is known to be a relatively mobile element at high temperatures and LT-GaAs:Be may suffer from undesirable concentration-dependent diffusion at high doping levels. Here, we propose the use of C as an alternative p-type dopant in LT-GaAs. The combination of larger lattice concentration and superior thermal stability should make LT:GaAs:C a promising technology for radiation-hard field effect transistor (FET) applications. The proposed technology will offer enhancement in radiation hardness, thermal stability and reliability of III-V semiconductor-based field effect transistors compared to conventional undoped and Be-doped low-temperature buffers.