Tunneling through ultrathin GaAs n⁺⁺-p⁺⁺-n⁺⁺ barrier grown by molecular layer epitaxy

The l-V characteristics of ultrathin GaAs n⁺⁺-p⁺⁺-n⁺⁺ barrier structures with a 45 Å thick p⁺⁺ layer grown by molecular layer epitaxy (MLE) have been measured at room temperature and 77 K. The tunneling probability for this structure has been calculated as a function of effective tunneling width. It was found that good agreement between experiment and calculation is obtained when the effective tunneling width is assumed to be 75 A, which is much smaller than the depletion width about 190 A measured by C-V method. This fact indicates that the depletion width approximation cannot be used to measure the exact tunneling width for ultrathin barrier devices.