Scanning probe microscopy assisted local anodic oxidation offers advantages over other semiconductor fabrication techniques as it is a low contamination method. We demonstrate the fabrication of deep and highly reproducible nanohole arrays on InP using local anodic oxidation. Nanohole and nano-oxide mound radius and depth are controlled independently by altering atomic force microscope tip bias and humidity, with a maximum nanohole depth of 15.6 ± 1.2 nm being achieved. Additionally, the effect of tip write speed on oxide line formation is compared for n-type, p-type and semi-insulating substrates, which shows that n-type InP oxidises at a slower rate that semi-insulated or p-type InP. Finally, we calculate the activation energy for LAO of semi-insulating InP to be 0.4 eV, suggesting the oxidation mechanism is similar to that which occurs during plasma oxidation.