Rating of power diode can be increased by :

 Rating of power diode can be increased by introducing a drift layer in the diode between p and n sides. Where p and n side are heavily doped and drift layer (n-) is lightly doped. During reverse bias condition because of this doping difference more depletion layer is formed. Because p+ (holes) are heavily doped and can form small space of depletion layer, while during n-  side due to lightly doped it forms a free region. So that depletion region increases. So depletion region is more in n- side. Any  signal device can be converted to high power device.  By using same method, first we should identify the region  which blocks  voltages and then add a lightly doped layer on one of it’s side. (i.e., a junction which forms between heavily and lightly doped layers can block the high voltages. So by increase in the width of depletion region the drift layer increases, by increase in drift layer rating of power semi conductors are increased.