Structural and electrical properties of Au-TiB _x -nn ⁺ n ⁺⁺-InP and TiB _x -nn ⁺ n ⁺⁺-InP multilayer barrier structures on standard ("rigid") and soft ("porous")n ⁺⁺-InP substrates have been studied, with the semiconductor layers deposited by vapor-phase epitaxy, metallic layers formed by magnetron sputtering, and porous substrates fabricated by electrochemical etching of the standard InP. Samples on porous substrates have the following advantages: leakage currents in their reverse current-voltage characteristics are ten times lower; the range of the exponential rise in current in the forward characteristics is an order of magnitude wider; the changes in the ideality factor and the Schottky barrier height, observed as the contact area varies by a factor of 100, are three and 10 times smaller, respectively; and the structure of the layers is more stable in annealing at up to 800°C.