n-GaPp-(InSb)1-x(Sn2)x (0  х  0.05) heterostructures were fabricated and their current-voltage characteristics were studied. At low voltages V < 0.5 V the current-voltage characteristic is described by the exponential law: I = I0exp (qV / ckT) with an exponent c = 3.6, and at large voltage from 0.5 to 1.8 V by power laws: I = AVm with different values of coefficient A and exponent m at various voltages. At higher voltages - from 2.10 to 2.48 V a sublinear section is observed, it is described by the law: V = V0exp(Iad / S). The results are explained by the diffusion-drift mechanism of current transport conditions of dielectric relaxation, as well as the effect of injection depletion.