Planar channeling effects on the threshold voltage uniformity of GaAs metal‐semiconductor field‐effect transistors within 3‐in. GaAs wafers have been investigated using the stereographic projection method. This method is very useful for a quantitative understanding of the angular relationship between the direction of an incident ion beam and wafer orientation during implantation. The ratioN(X1)/N(X2) of the peak carrier concentration at a depth ofX1to the carrier concentration of a depth ofX2=2X1, obtained from the carrier depth profiles, was employed as a suitable parameter which effectively reflects the variation in the carrier profiles arising from the planar channeling effects. The conclusion, that the most uniform implants are attained at an azimuthal angle of 26.5° when tilting the wafer 10°, was analytically derived from the stereographic projection method and was experimentally confirmed.