Hello Geoffrey and All,
   
   
    I am not very sure about intrinsic carrier concentration ni.
    For any given temperature, the ni X ni = constant?
    Let's say for Temperature T1,
    the electron concentration carrier is n1
    while hole concentration carrier is p1
    then p1 X n1 = ni X ni
   
   
    Then Temperature T2,
    the electron concentration carrier is n2
    while hole concentration carrier is p2
    then p2 X n2 = ni X ni
   
    then for any Temperature Tx, px X nx is always equal to ni X ni , is
    it correct?
   
    Case 2
    When a p type Silicon(with dopant 10e17) is excite by light, the
    electron concentration n(initial) will increase to some n(excite)
    value.
   
    Is it true that n(initial) X 10e17 = ni X ni
    then n(excite) X 10e17 = ni X ni
   
    So it is true that for any time decay for carrier concentration
    the n(excite1,2,3,..) X 10e17 = ni X ni =n(initial) X 10e17  ?
   
    Thank you for any help given.
   
    rgds
    jason

Thank you Geoffrey!