| Summary: | The electrical characteristics of III-V semiconductors and their related structures have been investigated as a function of temperature and hydrostatic pressure. Bulk InP and GaAs samples have been examined over a wide range of impurity concentrations. The two dimensional electron gas (2DEG) confined in In0.53Ga0.47As at its interface with InP has been investigated in hetrojunction and multiple quantum well samples. The experimental Hall mobilities for nominally pure InP and GaAs are in good agreement with those calculated using an iterative solution of the Boltzman equation (ISBE). The activation energies of the shallow impurities present in the samples studied, as deduced from the temperature dependence of the carrier concentration, are in excellent agreement with theory. For the doped InP and GaAs samples the standard model was inadequate and could not describe the measured mobilities. For intermediately doped samples good agreement with experiment was obtained using a two band model, which included conduction via extended states as described by the ISBE together with hopping conduction in an impurity band. The experimental results for the heavily doped samples were found to fit a model for scattering from a correlated distribution of ionized impurities. The carrier concentration of the 2DEG in the hetrojunction samples had an unexpected pressure dependence at 300K. This data was found to be consistent with a pressure dependence of the conduction band offsets of -4+/-1meV/kbar. The temperature dependence of the pressure coefficient of the mobility for the 2DEG in InGaAs was in agreement with theory when the uncertainty in the pressure dependence of the effective mass was taken into account.
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