Impurity Conduction in Silicon Carbide

Abstract

We report on admittance spectroscopy (AS) investigations taken on aluminum (Al)- doped 6H-SiC crystals at low temperatures. Admittance spectra taken on Schottky contacts of highly doped samples (NA ≥ 7.2×1017 cm-3) reveal two series of conductance peaks, which cause two different slopes of the Arrhenius plot. The steep slope is attributed to the Al acceptor, while the flatter one - obtained from the low temperature peaks - is attributed to the activation energy ε3 of nearest neighbor hopping. We propose a model, which explains the unexpected sharpness of the low temperature conductance peaks and the disappearance of these peaks for low acceptor concentrations. The model is verified by simulation, and the AS results are compared with corresponding results obtained from resistivity measurements taken on 4H- and the identical 6HSiC samples.

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

“…[2][3][4] To reduce the resistivity, it is crucial to understand the underlying conduction mechanisms in these materials. The electrical-transport properties of heavily Al-implanted 4H-SiC layers, [5][6][7][8] Al-doped 6H-SiC wafers, 9,10) and Al-doped 4H-SiC epilayers 11) have been reported. Additionally, we investigated the temperature dependence of the resistivity [ ρ(T )] in heavily Al-doped 4H-SiC epilayers.…”

“…The method used to obtain a reliable ρ(T ) was reported elsewhere. 19) The well-known conduction mechanisms in semiconductors include band conduction, nearest-neighbor-hopping (NNH) conduction, 9,10,[20][21][22][23][24][25][26][27] and variable-range-hopping (VRH) conduction. [21][22][23][27][28][29][30][31][32] In the case that the currents due to band, NNH, and VRH conductions flow completely in parallel in the valence band, the Al acceptor level (E Al ), and the Fermi level [E F (T )], respectively, ρ(T ) can be expressed as…”

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

“…θ − 2θ patterns) were measured by using a high-resolution XRD system (SLX-2000, RIGAKU). The well-known conduction mechanisms in semiconductors include band conduction, NNH conduction, 9,10,[25][26][27][28][29][30][31][32] and VRH conduction. [26][27][28][32][33][34][35][36][37] If the currents due to band, NNH, and VRH conduction flow in parallel in the VB, at an Al acceptor level (E Al ), and around E F , respectively, the overall temperature-dependent resistivity [i.e.…”

“…[2][3][4] Understanding the underlying conduction mechanisms is essential for reducing the resistance of these materials. The electrical transport properties of heavily Al-implanted 4H-SiC layers, [5][6][7][8] heavily Al-doped 6H-SiC samples grown by physical vapor transport (PVT), 9,10) and heavily Al-doped 4H-SiC epilayers grown by CVD 11) have been reported. We have investigated the temperature dependence of resistivity [ρ(T)] for heavily Al-doped 4H-SiC epilayers grown by CVD.…”

“…1. At (C Al − C N ) values of around 2 × 10 19 cm −3 in Fig.1, the ρ(300) values for the PVT-grown codoped samples are still slightly higher than those for the CVD-grown samples.Figure2shows Arrhenius plots of ρ(T) for the CVD-grown samples with C Al values of 2.4 × 10 19 and 3.4 × 10 19 cm −3 (▿ and ◯, respectively), and for the PVT-grown codoped sample with C Al of 3.0 × 10 19 cm −3 and C N of 2.9 × 10 18 cm −3 (•).The well-known conduction mechanisms in semiconductors include band conduction, NNH conduction,9,10,[25][26][27][28][29][30][31][32] and VRH conduction [26][27][28][32][33][34][35][36][37]. If the currents due to band, NNH, and VRH conduction flow in parallel in the VB, at an Al acceptor level (E Al ), and around E F , respectively, the overall temperature-dependent resistivity [i.e.…”