Electrical Properties of Indium Phosphide Single Crystal Devices

Abstract

The electrical properties of zinc-doped indium phosphide single crystals which have been pulled from the melt by the liquid encapsulation Czochralski technique have been studied using aluminum and gold electrode combinations. Samples with aluminum electrodes showed ohmic conduction in the lower voltage range and two separate regions of space-charge-limited (SCL) conductivity at higher voltage levels controlled by a discrete trapping level and by an exponential distribution of traps above the valence band edge, respectively. Measurements of current density-temperature characteristics in the SCLC regions yielded voltage variable slopes on plots of the logarithm of current density as a function of the inverse temperature in accordance with the theory for exponential distribution of traps. On the other hand, constant slope was obtained for a single dominant level which immediately yielded its depth above the valence band edge. A number of parameters were evaluated on the basis of the theory of space-charge-limited conduction and the following values were obtained : excess acceptor concentration (Na –Nd) = 1.71018 m-3, discrete trap level E, = 0.20 eV above the valence band edge with a state density Nt(s) =2.2x1020m3, hole mobility μ = 7x10-3 m-2V-1s-1, room temperature hole