Dependence of conduction mechanisms in heavily Al-doped 4H-SiC epilayers on Al concentration

Abstract

To reduce the resistivity of heavily Al-doped 4H-SiC epilayers, the conduction mechanisms were investigated for Al concentrations (CAl) between 2.4 × 1019 and 4.7 × 1020 cm−3 and measurement temperatures (T) between 20 and 600 K. The results elucidated the relationship between the conduction mechanisms and the values of T and CAl. For the epilayers with CAl ∼ 3 × 1019 cm−3, an unexpected additional conduction mechanism was observed between the band and nearest-neighbor-hopping conduction regions, for which two plausible conduction models are proposed. To reduce the resistivity of epilayers with CAl > 2 × 1020 cm−3, it is essential to fabricate samples with low lattice distortion.

Transition of conduction mechanism from band to variable-range hopping conduction due to Al doping in heavily Al-doped 4H-SiC epilayers

“…We have also investigated the temperature dependence of resistivity [ρ(T)] for heavily Al-doped 4H-SiC epilayers. 11,12) We reported that in epilayers with Al concentrations (C Al ) of ⩽1.5 × 10 20 cm −3 the dominant conduction mechanisms at high and low temperatures were band and nearest-neighbor hopping (NNH) conduction, respectively, and in epilayers with C Al values of ⩾2.4 × 10 20 cm −3 the dominant conduction mechanism was variable-range hopping (VRH) conduction over the entire range of measurement temperatures examined. 12) In this study, we investigated the transition of the conduction mechanism from band and NNH conduction to VRH conduction at C Al values of approximately 2 × 10 20 cm −3 .…”

Research progress of large size SiC single crystal materials and devices

“…N-channel SiC Based IGBT devices is considered to be one of the most promising electronic devices, because it has low resistance features in the high-voltage field because of the conductance modulation. In order to manufacture high capability n-channel IGBT, p-type SiC substrates are needed as the injector region [12][13][14] .…”

Comparison of temperature-dependent resistivity of heavily Al- and N-codoped 4H-SiC grown by physical vapor transport and heavily Al-doped 4H-SiC grown by chemical vapor deposition

“…We have investigated the temperature dependence of resistivity [ρ(T)] for heavily Al-doped 4H-SiC epilayers grown by CVD. [12][13][14][15][16][17][18][19][20][21] Based on ρ(T) for heavily Al-doped 4H-SiC epilayers, in epilayers with Al concentrations (C Al ) of ⩽1.5 × 10 20 cm −3 , the dominant conduction mechanisms at high and low temperatures are band and nearest-neighbor hopping (NNH) conduction, respectively. 13,14) In epilayers with C Al values of ⩾1.8 × 10 20 cm −3 , the dominant conduction mechanisms at high and low temperatures are band and variable-range hopping (VRH) conduction, respectively.…”

“…[12][13][14][15][16][17][18][19][20][21] Based on ρ(T) for heavily Al-doped 4H-SiC epilayers, in epilayers with Al concentrations (C Al ) of ⩽1.5 × 10 20 cm −3 , the dominant conduction mechanisms at high and low temperatures are band and nearest-neighbor hopping (NNH) conduction, respectively. 13,14) In epilayers with C Al values of ⩾1.8 × 10 20 cm −3 , the dominant conduction mechanisms at high and low temperatures are band and variable-range hopping (VRH) conduction, respectively. 13,14,16) The growth rate of PVT-grown 4H-SiC epilayers is much higher than that of CVD-grown 4H-SiC epilayers, which makes the fabrication cost of 4H-SiC lower.…”

“…13,14) In epilayers with C Al values of ⩾1.8 × 10 20 cm −3 , the dominant conduction mechanisms at high and low temperatures are band and variable-range hopping (VRH) conduction, respectively. 13,14,16) The growth rate of PVT-grown 4H-SiC epilayers is much higher than that of CVD-grown 4H-SiC epilayers, which makes the fabrication cost of 4H-SiC lower. However, the 4H-SiC polytype is not stabilized through Al doping by PVT alone, 22) whereas codoping of Al and N stabilizes the 4H-SiC polytype even for heavily Al-doped 4H-SiC grown by PVT.…”