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 2·10 3 ≤ ρ D0 ≤9·10 6 Ω·cm at 77 K and doped with erbium with 10 −5 ≤ N Er ≤10 −1 at.%. It was found that its absolute value (| U T |), in addition to E ^ and T 0 , also depends on ρ D0 and N . In the non-doped samples with ρ D0 ≤1·10 4 Ω·cm and doped with N Er >10 −2 at.%, the dependence | U T | ( E ^ ) consists of successive sections: | U T | ∼ E ^ 2 ,   | U T | ∼ E ^ and | U T | ∼ E ^ 0.5 . In non-doped with ρ D0 ≥ 5·10 4 Ω·cm and alloyed with 10 −5 ≤ N Er ≤ 10 −2 at.% samples at T 0 < 250 K and low-heating E ^ dependence | U T | ( E ^ ) obeys the law | U T | ∼ E ^ κ 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 T 0 >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 T 0 , the dependence | U T | ( 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 T 0 <250 K, the influence of random macroscopic defects must also be taken into account. A qualitative explanation of the results is proposed.