Tunnelling currents in very thin planar-doped barrier n⁺-i-p⁺-i-n⁺ structures

The GaAs planar doped barrier (PDB) n⁺-i-p⁺-i-n⁺ structures with different barrier heights and thicknesses are fabricated by the molecular layer epitaxy (MLE) method. The tunnelling probabilities of these structures are calculated, based on the triangular potential barrier model, using WKB approximation. The calculated tunnelling currents for the PDB structures with designed source-drain distances of 460 angstroms and 1000 angstroms are in good agreement with the experimental data at 40 K to approximately 173 K and 40 K to approximately 77 K, respectively. This indicates that the dominant transport mechanism in these structures is tunnelling in these temperature regions. The current transport in the thinner PDB structures with metallurgical source-drain distances of 110 angstroms is dominated by tunnelling even at room temperature, but modelling of I-V characteristics for such thin structures should account for the n⁺ layer's depletion.