I'm an analog microelectronics designer who wants to know a little more about why strain modifies the mobility of semiconductors. I've found a paper by Nidhi Mohta and Scott Thompson where they show a three-dimensional coordinate system where the axis are labelled Kx, Ky and Kz. In addition, they have drawn ellipsoids whose shapes are modified when the semiconductor is strained. Unfortunately, they don't say anything about how this figure has been derived. I've tracked down other papers on the same subject, but they also start with this rather nice drawing without telling how they arrived at it. Can someone please explain without resorting to difficult equations the diagram with the ellipsoids? An intuitive explanation on what happens to a semiconductor when it is strained would also be greatly appreciated. Thanks a lot in advance.