Thermal reliability of deuterated AlGaN/GaN HEMTs

The reliability of the deuterated AlGaN/GaN High Electron Mobility Transistor (HEMT), which has an improved performance due to the deuterium passivation of point and extended defects, has been studied and compared to that of as-grown (non-deuterated), otherwise identical devices. The HEMT structure was grown by molecular beam epitaxy on Si substrates, and deuterium was in-diffused between the source and drain contacts, prior to the deposition of the gate. As-grown and deuterated transistors were simultaneously annealed at temperatures ranging from 300 degrees C to 700 degrees C, monitoring their charge transport properties after each anneal. It was observed that, even though both types of devices degraded, the degradation of the deuterated ones was less important. The evolution of their channel conductance reveals a different thermally stimulated degradation mechanism for each type of HEMT, with activation energies of 1.37 eV for the as-grown and 0.63 eV for the deuterated ones. Contrastingly, the pre-exponential term of the as-grown transistors was considerably higher than that of the deuterated ones, which explains their faster degradation. This study confirms that a proper deuteration improves the HEMT charge transport properties, making it more stable and reliable.