Systems and methods for plasma etching compound semiconductor (CS) dies and passively aligning the dies

Methods are provided for using masking techniques and plasma etching techniques to dice a compound semiconductor wafer into dies. Using these methods allows compound semiconductor die to be obtained that have smooth side walls, a variety of shapes and dimensions, and a variety of side wall profiles. In addition, by using these techniques to perform the dicing operations, the locations of features of the die relative to the side walls are ascertainable with certainty such that one or more of the side walls can be used as a passive alignment feature to precisely align one or more of the die with an external device.