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

The I-V characteristics of ultrathin GaAs n/sup ++/-p/sup ++/-n/sup ++/ barrier structures with a 45 /spl Aring/ thick p/sup ++/ 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 /spl Aring/, which is much smaller than the depletion width about 190 /spl Aring/ 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.