Why n*p always equal to ni square?? (semiconductor) Hi, For you guys who studied semiconductor physics must be familiar with the equation: np=ni2 I can understand why this is true for the intrinsic case (the broken bonds would always provide electron and hole in pairs ) But why is this still true for dopped semiconductors? Take Si for example, n=p=ni=1010 in intrinsic case (that's we all know). However, if dope 1015 Nd into the material, then n~1015 and p~105. The highlighted part is my confusion! Why p become smaller? Where do the holes go? Thanks for helping!