Effect of Pressure on the Energy Levels of Impurities in Semiconductors. II. Gold in Silicon

The changes in resistivity of silicon samples containing gold impurity, which are appropriately counterdoped with hydrogenic impurities, have been measured at hydrostatic pressures up to 30 000 kg cm^-2 near room temperature. The changes are explained by a dependence on pressure of the ionization energy of the gold impurity.The pressure coefficient of the energy of a gold acceptor level near the center of the forbidden gap has been determined, relative to both band edges; the coefficient of the separation from the conduction band edge is twice that of the separation from the valence band. The sum of the two coefficients gives a pressure coefficient for the total energy gap of -1.5×{}10^-6 eV kg^-1 cm² between 0 and 4000 kg cm^-2 or -2.4×{}10^-6 eV kg^-1 cm² near 20 000 kg cm^-2. The low-pressure value is in agreement with previous, more direct, determinations. A donor level due to the gold, roughly 0.35 eV above the valence band edge, has a very low pressure coefficient relative to that edge.