The effect of high pressure on S and Te-doped GaAs1-xPx

The pressure dependence of the electrical resistivity of n-type GaAs l -x Px is measured to a pressure of 7 kilobars at temperatures of 770, 195 0 , and 300 0 K. The samples are doped with sulfur and tellurium and have carrier concentrations in the 10^18 - 10^19 range. Changes in the resistivity as large as four orders of magnitude are observed at 77 0K for samples in the composition range 0.30 ~ x ~ 0.4~ The behavior of the samples is consistent with a model in which the higher lying [lOOJ conduction band edge has associated with it a donor level which is deep with respect to the [lOOJ minima. The level depth with respect to these minima is found to be 0.03 eV for Te-doped crystals, and ~ 0.06 eV for S-doped crystals. The S-doped samples also exhibit a light-sensitive, longlifetime trapping behavior. The trapping appears to be associated with an additional deep level which moves away from the [OOOJ conduction band minimum at the ratJ of approximately 10.8 x 10-3 eV/kbar. The data indicate that this trapping level is probably a second split-off level associated with and - 0.16 eV below the The mobility ratio of the two bands [equation] is found to be 15-30 at 3000K and 1950K but is found to increase to 60-100 at 77 0 K. The phosphorus concentration x at which the [OOOJ and [lOOJ minima are equal in energy appears to be x ~ 0.43 at 77 0K and x ~ 0.45 at 3000 K, implying that the separation between the minima increases with temperature at the rate of ~ 6 x 10-5 eV/oK. It is verified by combining resistance vs. pressure curves for samples of different composition x that increasing the pressure and increasing x have a similar effect on the band structure of the GaAs1-xPx system.U of I OnlyThesi