High carrier mobility on hydrogen terminated ⟨100⟩ diamond surfaces

An increase in carrier mobility from typical values around 100 to more than $300{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ at room temperature is detected on hydrogenated undoped $⟨100⟩$ diamond layers after annealing at 400 K in a vacuum. As a function of temperature in the range 400 to 125 K the high mobility followed tendencies remarkably close ionized impurity (toward low temperatures) and phonon scattering (toward high temperatures). As a function of annealing time, the high mobility increased with the time constant of about 6.8 h in the range of 1–16 h. A prerequisite for obtaining the largest increase in mobility was optimized surface cleanness. Exposing the samples to air resulted in a complete recovery of the original values of mobility, hole concentration, and conductivity after several days. The data are discussed in terms of interactions between holes in the surface conductive channel and adsorbates on the surface.