It was recalled that sharp fluctuations in carrier concentration, with small changes in the crystal stoichiometry of semi-insulating GaAs, had been recently considered. The fluctuations were there suggested to be a possible cause of variations in the performance of devices fabricated on semi-insulating GaAs substrates. This observation was based upon estimates using formation energies of point defects calculated by first-principles calculations. Since such calculations have inherent errors associated with them, it was unclear whether reported sharp fluctuations were artefacts which resulted from errors in formation-energy data. The results presented here showed, in spite of these errors, the sharp fluctuations in carrier concentrations were still predicted, further emphasizing the need to control strictly the crystal stoichiometry in order to avoid variations in device performance.

Effect of Uncertainty in Formation Energies of Defects in Calculations for Carrier Concentrations in Semi-Insulating GaAs. Deepak: Materials Science and Engineering B, 2003, 100[1], 102-5