1) Which one of the following materials is used for 'doping' to prepare P-type semiconductor :

2) Which one of the following materials is used for 'doping' to prepare N-type semiconductor :

3) The function of a diode can be compared with that of a :

4) The potential difference across a diode is termed as :

5) A semiconductor element in its pure form is called a/an _____ semiconductor and in its 'doped' form is called a/an _____ semiconductor :