Thermo-e.m.f. of hot current carriers in non-doped and doped crystals of a layered semiconductor n-InSe

Thermo-e.m.f. of hot current carriers is experimentally investigated in non-doped n-InSe crystals with a dark specific resistance of 2·10³≤ρ_D0≤9·10⁶Ω·cm at 77 K and doped with erbium with 10⁻⁵≤N_Er≤10⁻¹at.%. It was found that its absolute value (|U_T|), in addition to $\hat{E}$ and T₀, also depends on ρ_D0 and N. In the non-doped samples with ρ_D0≤1·10⁴Ω·cm and doped with N_Er>10⁻² at.%, the dependence $|{U}_{T}|(\hat{E})$ consists of successive sections: $|{U}_{T}|\sim {\hat{E}}^{2},}\quad|{U}_{T}|\sim \hat{E}$ and $|{U}_{T}|\sim {\hat{E}}^{0.5}$. In non-doped with ρ_D0≥ 5·10⁴ Ω·cm and alloyed with 10⁻⁵≤N_Er≤ 10⁻² at.% samples at T₀ < 250 K and low-heating $\hat{E}$ dependence $|{U}_{T}|(\hat{E})$ obeys the law $|{U}_{T}|\sim {\hat{E}}^{\kappa }$ with 2<κ≤5. The value of k monotonously depends on N_Er and reaches its maximum value at N_Er=5·10⁻⁴ at.%. At T₀ >250 K, in all the samples studied, as well as in non-doped low-resistance and doped with N_Er>10⁻² at.% samples for all T₀, the dependence $|{U}_{T}|(\hat{E})$ follows the theory of thermo-e.m.f. of hot current carriers in spatially homogeneous crystalline semiconductors. To explain the results in non-doped high-resistance and doped with 10⁻⁵≤N_Et≤10⁻² at.% samples at T₀<250 K, the influence of random macroscopic defects must also be taken into account. A qualitative explanation of the results is proposed.