The fabrication of aligned single-walled, carbon nanotube (SWCNT) intratube junction devices by partially coating pristine SWCNTs with a beta-nicotinamide adenine dinucleotide (NADH) solution and subsequent annealing at 150 C is reported. Gate-bias-dependent rectification behavior is observed with a rectification ratio of >10(3) at +/- 1 V. A comparative study with p-n-junction devices of randomly networked SWCNTs confirms the advantage of using aligned SWCNTs with substantially better rectifying characteristics due to the selective removal of metallic tubes by electrical breakdown. The gate dependence of the intratube p-n-junction in the forward and backward directions is attributed to the difference in the shift of the Fermi levels (forward bias) and the enhanced direct tunneling (reverse bias), as suggested by band-diagram modeling. This work suggests a potential application of aligned SWCNT intratube p-n-junction devices in the future of nanoelectronic circuits.