Electrical properties of donors in gallium phosphide

The thermal ionization energies of S, Te, and Si donors in GaP and their dependences on impurity concentration are determined from an anlysis of Hall effect data. An ellipsoidal six-valley model is used incorporating the effects of valley-orbit splitting of the ground state of the P-site donors. A careful characterization of the samples ensures that results are obtained on samples containing only one type of dominant donor. The thermal ionization energies of the above donors extrapolated to infinite dilution are (105.0 +- 5.7), (94.1 +- 2.6), and (83.5 +- 1.7) meV, respectively. The valley-orbit splitting energies of S and Te donors are also obtained, amounting to (34 +- 9) and (23.5 +- 9) meV, respectively. (author)