SOLUBILITY OF NITROGEN IN BINARY III-V SYSTEMS

A version of the valance-force-field (VFF) model has been developed sp ecifically for the calculation of the nitrogen solubility in conventio nal III-V binary compounds. At very low N concentrations, i.e., in the dilute limit, the atoms surrounding the N are allowed to relax. It is found that the energy due to bond stretching and bond bending is lowe red and the solubility limit is increased substantially when both subl attices are allowed to relax to distances as large as the sixth neares t neighbor positions. Using this model, the equilibrium mole fraction of N in GaP was calculated to be 6 x 10(-7) cm(-3) at 700 degrees C, w hich agrees with experimental data and closely approximates the result s of the semi-empirical delta-lattice parameter model. It is more than three orders of magnitude larger than the result obtained using the s implest VFF model with relaxation of only the first neighbor bonds. Ot her nitride systems such as GaAsN, AlPN, AlAsN, InPN, and InAsN were i nvestigated as well. The equilibrium mole fraction of nitrogen in InAs is the highest (about 0.002 at 700 degrees C). A miscibility gap is a lso predicted for the commercially important GaInN system.