The continuity equation governs the functional relationship of carrier concentrations for applied voltage (or) current inputs in the semiconductor body with time and distance. It is based on law of conservation of charge. The continuity equation for holes is given as
p/ t = ((p0-p)/tp) – (1/q)* Jp/ x
Where p is hole concentration which is function of distnce and time, p0 = g* tp,g is holes generated per volume due to thermal generation, Jp is hole current.The continuity eqaution is simlar for elctrons with p replaced by n.