Hydrogen desorption and ammonia adsorption on polycrystalline GaN surfaces

We have studied the D2 desorption and NH3 adsorption on polycrystalline GaN surfaces using time-of-flight detection of recoiled H+ and D+ ions. Two surface deuterium states characterized by different thermal stability are identified. Rate abalysis for isothermal D2 desorption is performed near 250°C, which we attribute to desorption from Ga sites. We assign the higher temperature D2 desorption state decomposing near 500°C to desorption from N sites. Both clean and D-terminated GaN surfaces are quite reactive towards NH3 adsorption. We observed that HD exchange during NH3 exposure occurs rapidly at room temperature.