thanseeq : construction of these diodes are same but it impurity concentration is different,
p-n diode - 1:10^7 (one impurity atom for 10^7 silicon atom)
zener diode - 1:10^5 (one impurity atom for 10^5 silicon atom)
tunnel diode -1:10^3 (one impurity atom for 10^3 silicon atom)

On : 2016-06-13