Electrical properties of nitrogen-doped GaP

The electrical properties, namely, electron concentration and mobility, have been investigated in the temperature range from 53 to 400 K for undoped and nitrogen-doped VPE GaP. The undoped GaP has a background doping level of ND∼1017 cm−3 and NA∼1016 cm−3. The donor ionization energies vary from 49 to 74 meV and are proportional to NA1/3. These data identify the background donor to be Si. The mobility of the nondoped material is approximately 150 cm2/V s at 300 K and is dependent on ND+NA at 77 K, varying between 377 and 1263 cm2/V s. NH3 is added to the system to incorporate nitrogen into the GaP. This is found to decrease ND to ∼2×1016 cm−3 and increase the donor ionization energy. This is attributed to reaction of the volatile Si species acting as dopant with NH3 to form Si3N4, thus reducing the Si concentration in the solid. The electron mobility at 77 K is also reduced by the addition of N to the solid. This is attributed to neutral impurity scattering by the nitrogen.