Hopping conduction range of heavily Al-doped 4H-SiC thick epilayers grown by CVD

摘要

To outline the hopping conduction range, the electrical characteristics of CVD-grown heavily Al-doped 4H-SiC thick epilayers (2.0 × 10~(19)-4.0 × 10~(20)cm~(-3)) were investigated in a wide temperature regime (20-900 K). It is found that, below 100K, hopping conduction dominates the carrier transport for all epilayers, and the corresponding hopping conduction activation energy shows a maximum of ～30 meV at around 1.1 × 10~(20) cm~(-3). With increasing doping level, the temperature dependence of resistivity evolves and finally obeys the ～1 /T~(1/4) law in the entire temperature regime, which gives direct evidence of variable-range hopping conduction.